Interactions Command Localization (#2395)

* Request headers (#2394)

* add support for per-request headers

* remove unnecessary usings

* Revert "remove unnecessary usings"

This reverts commit 8d674fe4fa.

* remove nullable strings from RequestOptions

* Add Localization Support to Interaction Service (#2211)

* add json and resx localization managers

* add utils class for getting command paths

* update json regex to make langage code optional

* remove IServiceProvider from ILocalizationManager method params

* replace the command path method in command map

* add localization fields to rest and websocket application command entity implementations

* move deconstruct extensions method to extensions folder

* add withLocalizations parameter to rest methods

* fix build error

* add rest conversions to interaction service

* add localization to the rest methods

* add inline docs

* fix implementation bugs

* add missing inline docs

* inline docs correction (Name/Description Localized properties)

* add choice localization

* fix conflicts

* fix conflicts

* add missing command props fields to ToApplicationCommandProps methods

* add locale parameter to Get*ApplicationCommandsAsync methods for fetching localized command names/descriptions

* Apply suggestions from code review

Co-authored-by: Armano den Boef <68127614+Rozen4334@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Armano den Boef <68127614+Rozen4334@users.noreply.github.com>

* Update src/Discord.Net.Core/Entities/Guilds/IGuild.cs

Co-authored-by: Armano den Boef <68127614+Rozen4334@users.noreply.github.com>

* add inline docs to LocalizationTarget

* fix upstream merge errors

* fix command parsing for context command names with space char

* fix command parsing for context command names with space char

* fix failed to generate buket id

* fix get guild commands endpoint

* update rexs localization manager to use single-file pattern

* Upstream Merge Localization Branch (#2434)

* fix ci/cd error (#2428)

* Fix role icon & emoji assignment. (#2416)

* Fix IGuild.GetBansAsync() (#2424)

fix the problem of not being able to get more than 1000 bans

* [DOCS] Add a note about `DontAutoRegisterAttribute`  (#2430)

* add a note about `DontAutoRegisterAttribute`

* Remove "to to" and add punctuation

Co-authored-by: MrCakeSlayer <13650699+MrCakeSlayer@users.noreply.github.com>

* fix: Missing Fact attribute in ColorTests (#2425)

* feat: Embed comparison (#2347)

* Fix broken code snippet in dependency injection docs (#2420)

* Fixed markdown formatting to show code snippet

* Fixed constructor injection code snippet pointer

* Added support for lottie stickers (#2359)

Co-authored-by: Armano den Boef <68127614+Rozen4334@users.noreply.github.com>
Co-authored-by: BokuNoPasya <49203428+1NieR@users.noreply.github.com>
Co-authored-by: Misha133 <61027276+Misha-133@users.noreply.github.com>
Co-authored-by: MrCakeSlayer <13650699+MrCakeSlayer@users.noreply.github.com>
Co-authored-by: Ge <gehongyan1996@126.com>
Co-authored-by: Charlie U <52503242+cpurules@users.noreply.github.com>
Co-authored-by: Kuba_Z2 <77853483+KubaZ2@users.noreply.github.com>

* remove unnecassary fields from ResxLocalizationManager

* update int framework guides

* remove space character tokenization from ResxLocalizationManager

Co-authored-by: Armano den Boef <68127614+Rozen4334@users.noreply.github.com>
Co-authored-by: BokuNoPasya <49203428+1NieR@users.noreply.github.com>
Co-authored-by: Misha133 <61027276+Misha-133@users.noreply.github.com>
Co-authored-by: MrCakeSlayer <13650699+MrCakeSlayer@users.noreply.github.com>
Co-authored-by: Ge <gehongyan1996@126.com>
Co-authored-by: Charlie U <52503242+cpurules@users.noreply.github.com>
Co-authored-by: Kuba_Z2 <77853483+KubaZ2@users.noreply.github.com>

docs/guides/int_framework/intro.md

@@ -376,6 +376,47 @@ respond to the Interactions within your command modules you need to perform the
 delegate can be used to create HTTP responses from a deserialized json object string.
 - Use the interaction endpoints of the module base instead of the interaction object (ie. `RespondAsync()`, `FollowupAsync()`...).
 
+## Localization
+
+Discord Slash Commands support name/description localization. Localization is available for names and descriptions of Slash Command Groups ([GroupAttribute]), Slash Commands ([SlashCommandAttribute]), Slash Command parameters and Slash Command Parameter Choices. Interaction Service can be initialized with an `ILocalizationManager` instance in its config which is used to create the necessary localization dictionaries on command registration. Interaction Service has two built-in `ILocalizationManager` implementations: `ResxLocalizationManager` and `JsonLocalizationManager`.
+
+### ResXLocalizationManager
+
+`ResxLocalizationManager` uses `.` delimited key names to traverse the resource files and get the localized strings (`group1.group2.command.parameter.name`). A `ResxLocalizationManager` instance must be initialized with a base resource name, a target assembly and a collection of `CultureInfo`s. Every key path must end with either `.name` or `.description`, including parameter choice strings. [Discord.Tools.LocalizationTemplate.Resx](https://www.nuget.org/packages/Discord.Tools.LocalizationTemplate.Resx) dotnet tool can be used to create localization file templates.
+
+### JsonLocalizationManager
+
+`JsonLocaliationManager` uses a nested data structure similar to Discord's Application Commands schema. You can get the Json schema [here](https://gist.github.com/Cenngo/d46a881de24823302f66c3c7e2f7b254). `JsonLocalizationManager` accepts a base path and a base file name and automatically discovers every resource file ( \basePath\fileName.locale.json ). A Json resource file should have a structure similar to:
+
+```json
+{
+    "command_1":{
+        "name": "localized_name",
+        "description": "localized_description",
+        "parameter_1":{
+            "name": "localized_name",
+            "description": "localized_description"
+        }
+    },
+    "group_1":{
+        "name": "localized_name",
+        "description": "localized_description",
+        "command_1":{
+            "name": "localized_name",
+             "description": "localized_description",
+             "parameter_1":{
+                 "name": "localized_name",
+                  "description": "localized_description"
+            },
+            "parameter_2":{
+                 "name": "localized_name",
+                  "description": "localized_description"
+            }
+        }
+    }
+}
+```
+
 [AutocompleteHandlers]: xref:Guides.IntFw.AutoCompletion
 [DependencyInjection]: xref:Guides.DI.Intro
 

src/Discord.Net.Core/Entities/Guilds/IGuild.cs

@@ -1194,12 +1194,17 @@ namespace Discord
         /// <summary>
         ///     Gets this guilds application commands.
         /// </summary>
+        /// <param name="withLocalizations">
+        ///     Whether to include full localization dictionaries in the returned objects,
+        ///     instead of the localized name and description fields.
+        /// </param>
+        /// <param name="locale">The target locale of the localized name and description fields. Sets the <c>X-Discord-Locale</c> header, which takes precedence over <c>Accept-Language</c>.</param>
         /// <param name="options">The options to be used when sending the request.</param>
         /// <returns>
         ///     A task that represents the asynchronous get operation. The task result contains a read-only collection
         ///     of application commands found within the guild.
         /// </returns>
-        Task<IReadOnlyCollection<IApplicationCommand>> GetApplicationCommandsAsync(RequestOptions options = null);
+        Task<IReadOnlyCollection<IApplicationCommand>> GetApplicationCommandsAsync(bool withLocalizations = false, string locale = null, RequestOptions options = null);
 
         /// <summary>
         ///     Gets an application command within this guild with the specified id.

src/Discord.Net.Core/Entities/Interactions/ApplicationCommandOption.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text.RegularExpressions;
@@ -12,6 +13,8 @@ namespace Discord
     {
         private string _name;
         private string _description;
+        private IDictionary<string, string> _nameLocalizations = new Dictionary<string, string>();
+        private IDictionary<string, string> _descriptionLocalizations = new Dictionary<string, string>();
 
         /// <summary>
         ///     Gets or sets the name of this option.
@@ -21,18 +24,7 @@ namespace Discord
             get => _name;
             set
             {
-                if (value == null)
-                    throw new ArgumentNullException(nameof(value), $"{nameof(Name)} cannot be null.");
-
-                if (value.Length > 32)
-                    throw new ArgumentOutOfRangeException(nameof(value), "Name length must be less than or equal to 32.");
-
-                if (!Regex.IsMatch(value, @"^[\w-]{1,32}$"))
-                    throw new FormatException($"{nameof(value)} must match the regex ^[\\w-]{{1,32}}$");
-
-                if (value.Any(x => char.IsUpper(x)))
-                    throw new FormatException("Name cannot contain any uppercase characters.");
-
+                EnsureValidOptionName(value);
                 _name = value;
             }
         }
@@ -43,12 +35,11 @@ namespace Discord
         public string Description
         {
             get => _description;
-            set => _description = value?.Length switch
+            set
             {
-                > 100 => throw new ArgumentOutOfRangeException(nameof(value), "Description length must be less than or equal to 100."),
-                0 => throw new ArgumentOutOfRangeException(nameof(value), "Description length must be at least 1."),
-                _ => value
-            };
+                EnsureValidOptionDescription(value);
+                _description = value;
+            }
         }
 
         /// <summary>
@@ -105,5 +96,72 @@ namespace Discord
         ///     Gets or sets the allowed channel types for this option.
         /// </summary>
         public List<ChannelType> ChannelTypes { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the localization dictionary for the name field of this option.
+        /// </summary>
+        /// <exception cref="ArgumentException">Thrown when any of the dictionary keys is an invalid locale.</exception>
+        public IDictionary<string, string> NameLocalizations
+        {
+            get => _nameLocalizations;
+            set
+            {
+                foreach (var (locale, name) in value)
+                {
+                    if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                        throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+                    EnsureValidOptionName(name);
+                }
+                _nameLocalizations = value;
+            }
+        }
+
+        /// <summary>
+        ///     Gets or sets the localization dictionary for the description field of this option.
+        /// </summary>
+        /// <exception cref="ArgumentException">Thrown when any of the dictionary keys is an invalid locale.</exception>
+        public IDictionary<string, string> DescriptionLocalizations
+        {
+            get => _descriptionLocalizations;
+            set
+            {
+                foreach (var (locale, description) in value)
+                {
+                    if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                        throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+                    EnsureValidOptionDescription(description);
+                }
+                _descriptionLocalizations = value;
+            }
+        }
+
+        private static void EnsureValidOptionName(string name)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name), $"{nameof(Name)} cannot be null.");
+
+            if (name.Length > 32)
+                throw new ArgumentOutOfRangeException(nameof(name), "Name length must be less than or equal to 32.");
+
+            if (!Regex.IsMatch(name, @"^[\w-]{1,32}$"))
+                throw new FormatException($"{nameof(name)} must match the regex ^[\\w-]{{1,32}}$");
+
+            if (name.Any(x => char.IsUpper(x)))
+                throw new FormatException("Name cannot contain any uppercase characters.");
+        }
+
+        private static void EnsureValidOptionDescription(string description)
+        {
+            switch (description.Length)
+            {
+                case > 100:
+                    throw new ArgumentOutOfRangeException(nameof(description),
+                        "Description length must be less than or equal to 100.");
+                case 0:
+                    throw new ArgumentOutOfRangeException(nameof(description), "Description length must at least 1.");
+            }
+        }
     }
 }

src/Discord.Net.Core/Entities/Interactions/ApplicationCommandOptionChoice.cs

@@ -1,4 +1,8 @@
 using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.RegularExpressions;
 
 namespace Discord
 {
@@ -9,6 +13,7 @@ namespace Discord
     {
         private string _name;
         private object _value;
+        private IDictionary<string, string> _nameLocalizations = new Dictionary<string, string>();
 
         /// <summary>
         ///     Gets or sets the name of this choice.
@@ -40,5 +45,33 @@ namespace Discord
                 _value = value;
             }
         }
+
+        /// <summary>
+        ///     Gets or sets the localization dictionary for the name field of this choice.
+        /// </summary>
+        /// <exception cref="ArgumentException">Thrown when any of the dictionary keys is an invalid locale.</exception>
+        public IDictionary<string, string> NameLocalizations
+        {
+            get => _nameLocalizations;
+            set
+            {
+                foreach (var (locale, name) in value)
+                {
+                    if (!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                        throw new ArgumentException("Key values of the dictionary must be valid language codes.");
+
+                    switch (name.Length)
+                    {
+                        case > 100:
+                            throw new ArgumentOutOfRangeException(nameof(value),
+                                "Name length must be less than or equal to 100.");
+                        case 0:
+                            throw new ArgumentOutOfRangeException(nameof(value), "Name length must at least 1.");
+                    }
+                }
+
+                _nameLocalizations = value;
+            }
+        }
     }
 }

src/Discord.Net.Core/Entities/Interactions/ApplicationCommandProperties.cs

@@ -1,3 +1,10 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using System.Text.RegularExpressions;
+
 namespace Discord
 {
     /// <summary>
@@ -5,6 +12,9 @@ namespace Discord
     /// </summary>
     public abstract class ApplicationCommandProperties
     {
+        private IReadOnlyDictionary<string, string> _nameLocalizations;
+        private IReadOnlyDictionary<string, string> _descriptionLocalizations;
+
         internal abstract ApplicationCommandType Type { get; }
 
         /// <summary>
@@ -17,6 +27,48 @@ namespace Discord
         /// </summary>
         public Optional<bool> IsDefaultPermission { get; set; }
 
+        /// <summary>
+        ///     Gets or sets the localization dictionary for the name field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> NameLocalizations
+        {
+            get => _nameLocalizations;
+            set
+            {
+                foreach (var (locale, name) in value)
+                {
+                    if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                        throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+                    Preconditions.AtLeast(name.Length, 1, nameof(name));
+                    Preconditions.AtMost(name.Length, SlashCommandBuilder.MaxNameLength, nameof(name));
+                    if (!Regex.IsMatch(name, @"^[\w-]{1,32}$"))
+                        throw new ArgumentException("Option name cannot contain any special characters or whitespaces!", nameof(name));
+                }
+                _nameLocalizations = value;
+            }
+        }
+
+        /// <summary>
+        ///     Gets or sets the localization dictionary for the description field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> DescriptionLocalizations
+        {
+            get => _descriptionLocalizations;
+            set
+            {
+                foreach (var (locale, description) in value)
+                {
+                    if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                        throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+                    Preconditions.AtLeast(description.Length, 1, nameof(description));
+                    Preconditions.AtMost(description.Length, SlashCommandBuilder.MaxDescriptionLength, nameof(description));
+                }
+                _descriptionLocalizations = value;
+            }
+        }
+
         /// <summary>
         ///     Gets or sets whether or not this command can be used in DMs.
         /// </summary>

src/Discord.Net.Core/Entities/Interactions/ContextMenus/MessageCommandBuilder.cs

@@ -1,3 +1,8 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.RegularExpressions;
+
 namespace Discord
 {
     /// <summary>
@@ -31,6 +36,11 @@ namespace Discord
         /// </summary>
         public bool IsDefaultPermission { get; set; } = true;
 
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> NameLocalizations => _nameLocalizations;
+
         /// <summary>
         ///     Gets or sets whether or not this command can be used in DMs.
         /// </summary>
@@ -42,6 +52,7 @@ namespace Discord
         public GuildPermission? DefaultMemberPermissions { get; set; }
 
         private string _name;
+        private Dictionary<string, string> _nameLocalizations;
 
         /// <summary>
         ///     Build the current builder into a <see cref="MessageCommandProperties"/> class.
@@ -86,6 +97,30 @@ namespace Discord
             return this;
         }
 
+        /// <summary>
+        ///     Sets the <see cref="NameLocalizations"/> collection.
+        /// </summary>
+        /// <param name="nameLocalizations">The localization dictionary to use for the name field of this command.</param>
+        /// <returns></returns>
+        /// <exception cref="ArgumentNullException">Thrown if <paramref name="nameLocalizations"/> is null.</exception>
+        /// <exception cref="ArgumentException">Thrown if any dictionary key is an invalid locale string.</exception>
+        public MessageCommandBuilder WithNameLocalizations(IDictionary<string, string> nameLocalizations)
+        {
+            if (nameLocalizations is null)
+                throw new ArgumentNullException(nameof(nameLocalizations));
+
+            foreach (var (locale, name) in nameLocalizations)
+            {
+                if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                    throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+                EnsureValidCommandName(name);
+            }
+
+            _nameLocalizations = new Dictionary<string, string>(nameLocalizations);
+            return this;
+        }
+
         /// <summary>
         ///     Sets whether or not this command can be used in dms
         /// </summary>
@@ -97,6 +132,41 @@ namespace Discord
             return this;
         }
 
+        /// <summary>
+        ///     Adds a new entry to the <see cref="NameLocalizations"/> collection.
+        /// </summary>
+        /// <param name="locale">Locale of the entry.</param>
+        /// <param name="name">Localized string for the name field.</param>
+        /// <returns>The current builder.</returns>
+        /// <exception cref="ArgumentException">Thrown if <paramref name="locale"/> is an invalid locale string.</exception>
+        public MessageCommandBuilder AddNameLocalization(string locale, string name)
+        {
+            if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+            EnsureValidCommandName(name);
+
+            _nameLocalizations ??= new();
+            _nameLocalizations.Add(locale, name);
+
+            return this;
+        }
+
+        private static void EnsureValidCommandName(string name)
+        {
+            Preconditions.NotNullOrEmpty(name, nameof(name));
+            Preconditions.AtLeast(name.Length, 1, nameof(name));
+            Preconditions.AtMost(name.Length, MaxNameLength, nameof(name));
+
+            // Discord updated the docs, this regex prevents special characters like @!$%(... etc,
+            // https://discord.com/developers/docs/interactions/slash-commands#applicationcommand
+            if (!Regex.IsMatch(name, @"^[\w-]{1,32}$"))
+                throw new ArgumentException("Command name cannot contain any special characters or whitespaces!", nameof(name));
+
+            if (name.Any(x => char.IsUpper(x)))
+                throw new FormatException("Name cannot contain any uppercase characters.");
+        }
+
         /// <summary>
         ///     Sets the default member permissions required to use this application command.
         /// </summary>

src/Discord.Net.Core/Entities/Interactions/ContextMenus/UserCommandBuilder.cs

@@ -1,3 +1,8 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.RegularExpressions;
+
 namespace Discord
 {
     /// <summary>
@@ -5,7 +10,7 @@ namespace Discord
     /// </summary>
     public class UserCommandBuilder
     {
-        /// <summary> 
+        /// <summary>
         ///     Returns the maximum length a commands name allowed by Discord.
         /// </summary>
         public const int MaxNameLength = 32;
@@ -31,6 +36,11 @@ namespace Discord
         /// </summary>
         public bool IsDefaultPermission { get; set; } = true;
 
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> NameLocalizations => _nameLocalizations;
+
         /// <summary>
         ///     Gets or sets whether or not this command can be used in DMs.
         /// </summary>
@@ -42,6 +52,7 @@ namespace Discord
         public GuildPermission? DefaultMemberPermissions { get; set; }
 
         private string _name;
+        private Dictionary<string, string> _nameLocalizations;
 
         /// <summary>
         ///     Build the current builder into a <see cref="UserCommandProperties"/> class.
@@ -84,6 +95,30 @@ namespace Discord
             return this;
         }
 
+        /// <summary>
+        ///     Sets the <see cref="NameLocalizations"/> collection.
+        /// </summary>
+        /// <param name="nameLocalizations">The localization dictionary to use for the name field of this command.</param>
+        /// <returns>The current builder.</returns>
+        /// <exception cref="ArgumentNullException">Thrown if <paramref name="nameLocalizations"/> is null.</exception>
+        /// <exception cref="ArgumentException">Thrown if any dictionary key is an invalid locale string.</exception>
+        public UserCommandBuilder WithNameLocalizations(IDictionary<string, string> nameLocalizations)
+        {
+            if (nameLocalizations is null)
+                throw new ArgumentNullException(nameof(nameLocalizations));
+
+            foreach (var (locale, name) in nameLocalizations)
+            {
+                if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                    throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+                EnsureValidCommandName(name);
+            }
+
+            _nameLocalizations = new Dictionary<string, string>(nameLocalizations);
+            return this;
+        }
+        
         /// <summary>
         ///     Sets whether or not this command can be used in dms
         /// </summary>
@@ -95,6 +130,41 @@ namespace Discord
             return this;
         }
 
+        /// <summary>
+        ///     Adds a new entry to the <see cref="NameLocalizations"/> collection.
+        /// </summary>
+        /// <param name="locale">Locale of the entry.</param>
+        /// <param name="name">Localized string for the name field.</param>
+        /// <returns>The current builder.</returns>
+        /// <exception cref="ArgumentException">Thrown if <paramref name="locale"/> is an invalid locale string.</exception>
+        public UserCommandBuilder AddNameLocalization(string locale, string name)
+        {
+            if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+            EnsureValidCommandName(name);
+
+            _nameLocalizations ??= new();
+            _nameLocalizations.Add(locale, name);
+
+            return this;
+        }
+
+        private static void EnsureValidCommandName(string name)
+        {
+            Preconditions.NotNullOrEmpty(name, nameof(name));
+            Preconditions.AtLeast(name.Length, 1, nameof(name));
+            Preconditions.AtMost(name.Length, MaxNameLength, nameof(name));
+
+            // Discord updated the docs, this regex prevents special characters like @!$%(... etc,
+            // https://discord.com/developers/docs/interactions/slash-commands#applicationcommand
+            if (!Regex.IsMatch(name, @"^[\w-]{1,32}$"))
+                throw new ArgumentException("Command name cannot contain any special characters or whitespaces!", nameof(name));
+
+            if (name.Any(x => char.IsUpper(x)))
+                throw new FormatException("Name cannot contain any uppercase characters.");
+        }
+
         /// <summary>
         ///     Sets the default member permissions required to use this application command.
         /// </summary>

src/Discord.Net.Core/Entities/Interactions/IApplicationCommand.cs

@@ -52,6 +52,32 @@ namespace Discord
         /// </summary>
         IReadOnlyCollection<IApplicationCommandOption> Options { get; }
 
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command.
+        /// </summary>
+        IReadOnlyDictionary<string, string> NameLocalizations { get; }
+
+        /// <summary>
+        ///     Gets the localization dictionary for the description field of this command.
+        /// </summary>
+        IReadOnlyDictionary<string, string> DescriptionLocalizations { get; }
+
+        /// <summary>
+        ///     Gets the localized name of this command.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        string NameLocalized { get; }
+
+        /// <summary>
+        ///     Gets the localized description of this command.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        string DescriptionLocalized { get; }
+
         /// <summary>
         ///     Modifies the current application command.
         /// </summary>

src/Discord.Net.Core/Entities/Interactions/IApplicationCommandOption.cs

@@ -71,5 +71,31 @@ namespace Discord
         ///     Gets the allowed channel types for this option.
         /// </summary>
         IReadOnlyCollection<ChannelType> ChannelTypes { get; }
+
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command option.
+        /// </summary>
+        IReadOnlyDictionary<string, string> NameLocalizations { get; }
+
+        /// <summary>
+        ///     Gets the localization dictionary for the description field of this command option.
+        /// </summary>
+        IReadOnlyDictionary<string, string> DescriptionLocalizations { get; }
+
+        /// <summary>
+        ///     Gets the localized name of this command option.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        string NameLocalized { get; }
+
+        /// <summary>
+        ///     Gets the localized description of this command option.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to true when requesting the command.
+        /// </remarks>
+        string DescriptionLocalized { get; }
     }
 }

src/Discord.Net.Core/Entities/Interactions/IApplicationCommandOptionChoice.cs

@@ -1,3 +1,5 @@
+using System.Collections.Generic;
+
 namespace Discord
 {
     /// <summary>
@@ -14,5 +16,18 @@ namespace Discord
         ///     Gets the value of the choice.
         /// </summary>
         object Value { get; }
+
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command option.
+        /// </summary>
+        IReadOnlyDictionary<string, string> NameLocalizations { get; }
+
+        /// <summary>
+        ///     Gets the localized name of this command option.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        string NameLocalized { get; }
     }
 }

src/Discord.Net.Core/Entities/Interactions/SlashCommands/SlashCommandBuilder.cs

@@ -1,6 +1,9 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
+using System.Net.Sockets;
 using System.Text.RegularExpressions;
 
 namespace Discord
@@ -31,18 +34,7 @@ namespace Discord
             get => _name;
             set
             {
-                Preconditions.NotNullOrEmpty(value, nameof(value));
-                Preconditions.AtLeast(value.Length, 1, nameof(value));
-                Preconditions.AtMost(value.Length, MaxNameLength, nameof(value));
-
-                // Discord updated the docs, this regex prevents special characters like @!$%(... etc,
-                // https://discord.com/developers/docs/interactions/slash-commands#applicationcommand
-                if (!Regex.IsMatch(value, @"^[\w-]{1,32}$"))
-                    throw new ArgumentException("Command name cannot contain any special characters or whitespaces!", nameof(value));
-
-                if (value.Any(x => char.IsUpper(x)))
-                    throw new FormatException("Name cannot contain any uppercase characters.");
-
+                EnsureValidCommandName(value);
                 _name = value;
             }
         }
@@ -55,10 +47,7 @@ namespace Discord
             get => _description;
             set
             {
-                Preconditions.NotNullOrEmpty(value, nameof(Description));
-                Preconditions.AtLeast(value.Length, 1, nameof(Description));
-                Preconditions.AtMost(value.Length, MaxDescriptionLength, nameof(Description));
-
+                EnsureValidCommandDescription(value);
                 _description = value;
             }
         }
@@ -76,6 +65,16 @@ namespace Discord
             }
         }
 
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> NameLocalizations => _nameLocalizations;
+
+        /// <summary>
+        ///     Gets the localization dictionary for the description field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> DescriptionLocalizations => _descriptionLocalizations;
+
         /// <summary>
         ///     Gets or sets whether the command is enabled by default when the app is added to a guild
         /// </summary>
@@ -93,6 +92,8 @@ namespace Discord
 
         private string _name;
         private string _description;
+        private Dictionary<string, string> _nameLocalizations;
+        private Dictionary<string, string> _descriptionLocalizations;
         private List<SlashCommandOptionBuilder> _options;
 
         /// <summary>
@@ -106,6 +107,8 @@ namespace Discord
                 Name = Name,
                 Description = Description,
                 IsDefaultPermission = IsDefaultPermission,
+                NameLocalizations = _nameLocalizations,
+                DescriptionLocalizations = _descriptionLocalizations,
                 IsDMEnabled = IsDMEnabled,
                 DefaultMemberPermissions = DefaultMemberPermissions ?? Optional<GuildPermission>.Unspecified
             };
@@ -190,13 +193,17 @@ namespace Discord
         /// <param name="isAutocomplete">If this option is set to autocomplete.</param>
         /// <param name="options">The options of the option to add.</param>
         /// <param name="channelTypes">The allowed channel types for this option.</param>
+        /// <param name="nameLocalizations">Localization dictionary for the name field of this command.</param>
+        /// <param name="descriptionLocalizations">Localization dictionary for the description field of this command.</param>
         /// <param name="choices">The choices of this option.</param>
         /// <param name="minValue">The smallest number value the user can input.</param>
         /// <param name="maxValue">The largest number value the user can input.</param>
         /// <returns>The current builder.</returns>
         public SlashCommandBuilder AddOption(string name, ApplicationCommandOptionType type,
            string description, bool? isRequired = null, bool? isDefault = null, bool isAutocomplete = false, double? minValue = null, double? maxValue = null,
-           int? minLength = null, int? maxLength = null, List<SlashCommandOptionBuilder> options = null, List<ChannelType> channelTypes = null, params ApplicationCommandOptionChoiceProperties[] choices)
+           List<SlashCommandOptionBuilder> options = null, List<ChannelType> channelTypes = null, IDictionary<string, string> nameLocalizations = null,
+           IDictionary<string, string> descriptionLocalizations = null,
+           int? minLength = null, int? maxLength = null, params ApplicationCommandOptionChoiceProperties[] choices)
         {
             Preconditions.Options(name, description);
 
@@ -226,6 +233,12 @@ namespace Discord
                 MaxLength = maxLength,
             };
 
+            if (nameLocalizations is not null)
+                option.WithNameLocalizations(nameLocalizations);
+
+            if (descriptionLocalizations is not null)
+                option.WithDescriptionLocalizations(descriptionLocalizations);
+
             return AddOption(option);
         }
 
@@ -268,6 +281,116 @@ namespace Discord
             Options.AddRange(options);
             return this;
         }
+
+        /// <summary>
+        ///     Sets the <see cref="NameLocalizations"/> collection.
+        /// </summary>
+        /// <param name="nameLocalizations">The localization dictionary to use for the name field of this command.</param>
+        /// <returns></returns>
+        /// <exception cref="ArgumentNullException">Thrown if <paramref name="nameLocalizations"/> is null.</exception>
+        /// <exception cref="ArgumentException">Thrown if any dictionary key is an invalid locale string.</exception>
+        public SlashCommandBuilder WithNameLocalizations(IDictionary<string, string> nameLocalizations)
+        {
+            if (nameLocalizations is null)
+                throw new ArgumentNullException(nameof(nameLocalizations));
+
+            foreach (var (locale, name) in nameLocalizations)
+            {
+                if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                    throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+                EnsureValidCommandName(name);
+            }
+
+            _nameLocalizations = new Dictionary<string, string>(nameLocalizations);
+            return this;
+        }
+
+        /// <summary>
+        ///     Sets the <see cref="DescriptionLocalizations"/> collection.
+        /// </summary>
+        /// <param name="descriptionLocalizations">The localization dictionary to use for the description field of this command.</param>
+        /// <returns></returns>
+        /// <exception cref="ArgumentNullException">Thrown if <paramref name="descriptionLocalizations"/> is null.</exception>
+        /// <exception cref="ArgumentException">Thrown if any dictionary key is an invalid locale string.</exception>
+        public SlashCommandBuilder WithDescriptionLocalizations(IDictionary<string, string> descriptionLocalizations)
+        {
+            if (descriptionLocalizations is null)
+                throw new ArgumentNullException(nameof(descriptionLocalizations));
+
+            foreach (var (locale, description) in descriptionLocalizations)
+            {
+                if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                    throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+                EnsureValidCommandDescription(description);
+            }
+
+            _descriptionLocalizations = new Dictionary<string, string>(descriptionLocalizations);
+            return this;
+        }
+
+        /// <summary>
+        ///     Adds a new entry to the <see cref="NameLocalizations"/> collection.
+        /// </summary>
+        /// <param name="locale">Locale of the entry.</param>
+        /// <param name="name">Localized string for the name field.</param>
+        /// <returns>The current builder.</returns>
+        /// <exception cref="ArgumentException">Thrown if <paramref name="locale"/> is an invalid locale string.</exception>
+        public SlashCommandBuilder AddNameLocalization(string locale, string name)
+        {
+            if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+            EnsureValidCommandName(name);
+
+            _nameLocalizations ??= new();
+            _nameLocalizations.Add(locale, name);
+
+            return this;
+        }
+
+        /// <summary>
+        ///     Adds a new entry to the <see cref="Description"/> collection.
+        /// </summary>
+        /// <param name="locale">Locale of the entry.</param>
+        /// <param name="description">Localized string for the description field.</param>
+        /// <returns>The current builder.</returns>
+        /// <exception cref="ArgumentException">Thrown if <paramref name="locale"/> is an invalid locale string.</exception>
+        public SlashCommandBuilder AddDescriptionLocalization(string locale, string description)
+        {
+            if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+            EnsureValidCommandDescription(description);
+
+            _descriptionLocalizations ??= new();
+            _descriptionLocalizations.Add(locale, description);
+
+            return this;
+        }
+
+        internal static void EnsureValidCommandName(string name)
+        {
+            Preconditions.NotNullOrEmpty(name, nameof(name));
+            Preconditions.AtLeast(name.Length, 1, nameof(name));
+            Preconditions.AtMost(name.Length, MaxNameLength, nameof(name));
+
+            // Discord updated the docs, this regex prevents special characters like @!$%(... etc,
+            // https://discord.com/developers/docs/interactions/slash-commands#applicationcommand
+            if (!Regex.IsMatch(name, @"^[\w-]{1,32}$"))
+                throw new ArgumentException("Command name cannot contain any special characters or whitespaces!", nameof(name));
+
+            if (name.Any(x => char.IsUpper(x)))
+                throw new FormatException("Name cannot contain any uppercase characters.");
+        }
+
+        internal static void EnsureValidCommandDescription(string description)
+        {
+            Preconditions.NotNullOrEmpty(description, nameof(description));
+            Preconditions.AtLeast(description.Length, 1, nameof(description));
+            Preconditions.AtMost(description.Length, MaxDescriptionLength, nameof(description));
+        }
     }
 
     /// <summary>
@@ -287,6 +410,8 @@ namespace Discord
 
         private string _name;
         private string _description;
+        private Dictionary<string, string> _nameLocalizations;
+        private Dictionary<string, string> _descriptionLocalizations;
 
         /// <summary>
         ///     Gets or sets the name of this option.
@@ -298,10 +423,7 @@ namespace Discord
             {
                 if (value != null)
                 {
-                    Preconditions.AtLeast(value.Length, 1, nameof(value));
-                    Preconditions.AtMost(value.Length, SlashCommandBuilder.MaxNameLength, nameof(value));
-                    if (!Regex.IsMatch(value, @"^[\w-]{1,32}$"))
-                        throw new ArgumentException("Option name cannot contain any special characters or whitespaces!", nameof(value));
+                    EnsureValidCommandOptionName(value);
                 }
 
                 _name = value;
@@ -318,8 +440,7 @@ namespace Discord
             {
                 if (value != null)
                 {
-                    Preconditions.AtLeast(value.Length, 1, nameof(value));
-                    Preconditions.AtMost(value.Length, SlashCommandBuilder.MaxDescriptionLength, nameof(value));
+                    EnsureValidCommandOptionDescription(value);
                 }
 
                 _description = value;
@@ -381,6 +502,16 @@ namespace Discord
         /// </summary>
         public List<ChannelType> ChannelTypes { get; set; }
 
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> NameLocalizations => _nameLocalizations;
+
+        /// <summary>
+        ///     Gets the localization dictionary for the description field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> DescriptionLocalizations => _descriptionLocalizations;
+
         /// <summary>
         ///     Builds the current option.
         /// </summary>
@@ -424,6 +555,8 @@ namespace Discord
                 ChannelTypes = ChannelTypes,
                 MinValue = MinValue,
                 MaxValue = MaxValue,
+                NameLocalizations = _nameLocalizations,
+                DescriptionLocalizations = _descriptionLocalizations,
                 MinLength = MinLength,
                 MaxLength = MaxLength,
             };
@@ -440,13 +573,17 @@ namespace Discord
         /// <param name="isAutocomplete">If this option supports autocomplete.</param>
         /// <param name="options">The options of the option to add.</param>
         /// <param name="channelTypes">The allowed channel types for this option.</param>
+        /// <param name="nameLocalizations">Localization dictionary for the description field of this command.</param>
+        /// <param name="descriptionLocalizations">Localization dictionary for the description field of this command.</param>
         /// <param name="choices">The choices of this option.</param>
         /// <param name="minValue">The smallest number value the user can input.</param>
         /// <param name="maxValue">The largest number value the user can input.</param>
         /// <returns>The current builder.</returns>
         public SlashCommandOptionBuilder AddOption(string name, ApplicationCommandOptionType type,
            string description, bool? isRequired = null, bool isDefault = false, bool isAutocomplete = false, double? minValue = null, double? maxValue = null,
-           int? minLength = null, int? maxLength = null, List<SlashCommandOptionBuilder> options = null, List<ChannelType> channelTypes = null, params ApplicationCommandOptionChoiceProperties[] choices)
+           List<SlashCommandOptionBuilder> options = null, List<ChannelType> channelTypes = null, IDictionary<string, string> nameLocalizations = null,
+           IDictionary<string, string> descriptionLocalizations = null,
+           int? minLength = null, int? maxLength = null, params ApplicationCommandOptionChoiceProperties[] choices)
         {
             Preconditions.Options(name, description);
 
@@ -473,9 +610,15 @@ namespace Discord
                 Options = options,
                 Type = type,
                 Choices = (choices ?? Array.Empty<ApplicationCommandOptionChoiceProperties>()).ToList(),
-                ChannelTypes = channelTypes
+                ChannelTypes = channelTypes,
             };
 
+            if(nameLocalizations is not null)
+                option.WithNameLocalizations(nameLocalizations);
+
+            if(descriptionLocalizations is not null)
+                option.WithDescriptionLocalizations(descriptionLocalizations);
+
             return AddOption(option);
         }
         /// <summary>
@@ -522,10 +665,11 @@ namespace Discord
         /// </summary>
         /// <param name="name">The name of the choice.</param>
         /// <param name="value">The value of the choice.</param>
+        /// <param name="nameLocalizations">The localization dictionary for to use the name field of this command option choice.</param>
         /// <returns>The current builder.</returns>
-        public SlashCommandOptionBuilder AddChoice(string name, int value)
+        public SlashCommandOptionBuilder AddChoice(string name, int value, IDictionary<string, string> nameLocalizations = null)
         {
-            return AddChoiceInternal(name, value);
+            return AddChoiceInternal(name, value, nameLocalizations);
         }
 
         /// <summary>
@@ -533,10 +677,11 @@ namespace Discord
         /// </summary>
         /// <param name="name">The name of the choice.</param>
         /// <param name="value">The value of the choice.</param>
+        /// <param name="nameLocalizations">The localization dictionary for to use the name field of this command option choice.</param>
         /// <returns>The current builder.</returns>
-        public SlashCommandOptionBuilder AddChoice(string name, string value)
+        public SlashCommandOptionBuilder AddChoice(string name, string value, IDictionary<string, string> nameLocalizations = null)
         {
-            return AddChoiceInternal(name, value);
+            return AddChoiceInternal(name, value, nameLocalizations);
         }
 
         /// <summary>
@@ -544,10 +689,11 @@ namespace Discord
         /// </summary>
         /// <param name="name">The name of the choice.</param>
         /// <param name="value">The value of the choice.</param>
+        /// <param name="nameLocalizations">Localization dictionary for the description field of this command.</param>
         /// <returns>The current builder.</returns>
-        public SlashCommandOptionBuilder AddChoice(string name, double value)
+        public SlashCommandOptionBuilder AddChoice(string name, double value, IDictionary<string, string> nameLocalizations = null)
         {
-            return AddChoiceInternal(name, value);
+            return AddChoiceInternal(name, value, nameLocalizations);
         }
 
         /// <summary>
@@ -555,10 +701,11 @@ namespace Discord
         /// </summary>
         /// <param name="name">The name of the choice.</param>
         /// <param name="value">The value of the choice.</param>
+        /// <param name="nameLocalizations">The localization dictionary to use for the name field of this command option choice.</param>
         /// <returns>The current builder.</returns>
-        public SlashCommandOptionBuilder AddChoice(string name, float value)
+        public SlashCommandOptionBuilder AddChoice(string name, float value, IDictionary<string, string> nameLocalizations = null)
         {
-            return AddChoiceInternal(name, value);
+            return AddChoiceInternal(name, value, nameLocalizations);
         }
 
         /// <summary>
@@ -566,13 +713,14 @@ namespace Discord
         /// </summary>
         /// <param name="name">The name of the choice.</param>
         /// <param name="value">The value of the choice.</param>
+        /// <param name="nameLocalizations">The localization dictionary to use for the name field of this command option choice.</param>
         /// <returns>The current builder.</returns>
-        public SlashCommandOptionBuilder AddChoice(string name, long value)
+        public SlashCommandOptionBuilder AddChoice(string name, long value, IDictionary<string, string> nameLocalizations = null)
         {
-            return AddChoiceInternal(name, value);
+            return AddChoiceInternal(name, value, nameLocalizations);
         }
 
-        private SlashCommandOptionBuilder AddChoiceInternal(string name, object value)
+        private SlashCommandOptionBuilder AddChoiceInternal(string name, object value, IDictionary<string, string> nameLocalizations = null)
         {
             Choices ??= new List<ApplicationCommandOptionChoiceProperties>();
 
@@ -594,7 +742,8 @@ namespace Discord
             Choices.Add(new ApplicationCommandOptionChoiceProperties
             {
                 Name = name,
-                Value = value
+                Value = value,
+                NameLocalizations = nameLocalizations
             });
 
             return this;
@@ -724,5 +873,107 @@ namespace Discord
             Type = type;
             return this;
         }
+
+        /// <summary>
+        ///     Sets the <see cref="NameLocalizations"/> collection.
+        /// </summary>
+        /// <param name="nameLocalizations">The localization dictionary to use for the name field of this command option.</param>
+        /// <returns>The current builder.</returns>
+        /// <exception cref="ArgumentNullException">Thrown if <paramref name="nameLocalizations"/> is null.</exception>
+        /// <exception cref="ArgumentException">Thrown if any dictionary key is an invalid locale string.</exception>
+        public SlashCommandOptionBuilder WithNameLocalizations(IDictionary<string, string> nameLocalizations)
+        {
+            if (nameLocalizations is null)
+                throw new ArgumentNullException(nameof(nameLocalizations));
+
+            foreach (var (locale, name) in nameLocalizations)
+            {
+                if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                    throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+                EnsureValidCommandOptionName(name);
+            }
+
+            _nameLocalizations = new Dictionary<string, string>(nameLocalizations);
+            return this;
+        }
+
+        /// <summary>
+        ///     Sets the <see cref="DescriptionLocalizations"/> collection.
+        /// </summary>
+        /// <param name="descriptionLocalizations">The localization dictionary to use for the description field of this command option.</param>
+        /// <returns>The current builder.</returns>
+        /// <exception cref="ArgumentNullException">Thrown if <paramref name="descriptionLocalizations"/> is null.</exception>
+        /// <exception cref="ArgumentException">Thrown if any dictionary key is an invalid locale string.</exception>
+        public SlashCommandOptionBuilder WithDescriptionLocalizations(IDictionary<string, string> descriptionLocalizations)
+        {
+            if (descriptionLocalizations is null)
+                throw new ArgumentNullException(nameof(descriptionLocalizations));
+
+            foreach (var (locale, description) in _descriptionLocalizations)
+            {
+                if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                    throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+                EnsureValidCommandOptionDescription(description);
+            }
+
+            _descriptionLocalizations = new Dictionary<string, string>(descriptionLocalizations);
+            return this;
+        }
+
+        /// <summary>
+        ///     Adds a new entry to the <see cref="NameLocalizations"/> collection.
+        /// </summary>
+        /// <param name="locale">Locale of the entry.</param>
+        /// <param name="name">Localized string for the name field.</param>
+        /// <returns>The current builder.</returns>
+        /// <exception cref="ArgumentException">Thrown if <paramref name="locale"/> is an invalid locale string.</exception>
+        public SlashCommandOptionBuilder AddNameLocalization(string locale, string name)
+        {
+            if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+            EnsureValidCommandOptionName(name);
+
+            _descriptionLocalizations ??= new();
+            _nameLocalizations.Add(locale, name);
+
+            return this;
+        }
+
+        /// <summary>
+        ///     Adds a new entry to the <see cref="DescriptionLocalizations"/> collection.
+        /// </summary>
+        /// <param name="locale">Locale of the entry.</param>
+        /// <param name="description">Localized string for the description field.</param>
+        /// <returns>The current builder.</returns>
+        /// <exception cref="ArgumentException">Thrown if <paramref name="locale"/> is an invalid locale string.</exception>
+        public SlashCommandOptionBuilder AddDescriptionLocalization(string locale, string description)
+        {
+            if(!Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                throw new ArgumentException($"Invalid locale: {locale}", nameof(locale));
+
+            EnsureValidCommandOptionDescription(description);
+
+            _descriptionLocalizations ??= new();
+            _descriptionLocalizations.Add(locale, description);
+
+            return this;
+        }
+
+        private static void EnsureValidCommandOptionName(string name)
+        {
+            Preconditions.AtLeast(name.Length, 1, nameof(name));
+            Preconditions.AtMost(name.Length, SlashCommandBuilder.MaxNameLength, nameof(name));
+            if (!Regex.IsMatch(name, @"^[\w-]{1,32}$"))
+                throw new ArgumentException("Option name cannot contain any special characters or whitespaces!", nameof(name));
+        }
+
+        private static void EnsureValidCommandOptionDescription(string description)
+        {
+            Preconditions.AtLeast(description.Length, 1, nameof(description));
+            Preconditions.AtMost(description.Length, SlashCommandBuilder.MaxDescriptionLength, nameof(description));
+        }
     }
 }

src/Discord.Net.Core/Extensions/GenericCollectionExtensions.cs

@@ -0,0 +1,15 @@
+using System.Linq;
+
+namespace System.Collections.Generic;
+
+internal static class GenericCollectionExtensions
+{
+    public static void Deconstruct<T1, T2>(this KeyValuePair<T1, T2> kvp, out T1 value1, out T2 value2)
+    {
+        value1 = kvp.Key;
+        value2 = kvp.Value;
+    }
+
+    public static Dictionary<T1, T2> ToDictionary<T1, T2>(this IEnumerable<KeyValuePair<T1, T2>> kvp) =>
+        kvp.ToDictionary(x => x.Key, x => x.Value);
+}

src/Discord.Net.Core/IDiscordClient.cs

@@ -155,12 +155,14 @@ namespace Discord
         /// <summary>
         ///     Gets a collection of all global commands.
         /// </summary>
+        /// <param name="withLocalizations">Whether to include full localization dictionaries in the returned objects, instead of the name localized and description localized fields.</param>
+        /// <param name="locale">The target locale of the localized name and description fields. Sets <c>X-Discord-Locale</c> header, which takes precedence over <c>Accept-Language</c>.</param>
         /// <param name="options">The options to be used when sending the request.</param>
         /// <returns>
         ///     A task that represents the asynchronous get operation. The task result contains a read-only collection of global
         ///     application commands.
         /// </returns>
-        Task<IReadOnlyCollection<IApplicationCommand>> GetGlobalApplicationCommandsAsync(RequestOptions options = null);
+        Task<IReadOnlyCollection<IApplicationCommand>> GetGlobalApplicationCommandsAsync(bool withLocalizations = false, string locale = null, RequestOptions options = null);
 
         /// <summary>
         ///     Creates a global application command.

src/Discord.Net.Core/Net/Rest/IRestClient.cs

@@ -30,9 +30,13 @@ namespace Discord.Net.Rest
         /// <param name="cancelToken">The cancellation token used to cancel the task.</param>
         /// <param name="headerOnly">Indicates whether to send the header only.</param>
         /// <param name="reason">The audit log reason.</param>
+        /// <param name="requestHeaders">Additional headers to be sent with the request.</param>
         /// <returns></returns>
-        Task<RestResponse> SendAsync(string method, string endpoint, CancellationToken cancelToken, bool headerOnly = false, string reason = null);
-        Task<RestResponse> SendAsync(string method, string endpoint, string json, CancellationToken cancelToken, bool headerOnly = false, string reason = null);
-        Task<RestResponse> SendAsync(string method, string endpoint, IReadOnlyDictionary<string, object> multipartParams, CancellationToken cancelToken, bool headerOnly = false, string reason = null);
+        Task<RestResponse> SendAsync(string method, string endpoint, CancellationToken cancelToken, bool headerOnly = false, string reason = null,
+            IEnumerable<KeyValuePair<string, IEnumerable<string>>> requestHeaders = null);
+        Task<RestResponse> SendAsync(string method, string endpoint, string json, CancellationToken cancelToken, bool headerOnly = false, string reason = null,
+            IEnumerable<KeyValuePair<string, IEnumerable<string>>> requestHeaders = null);
+        Task<RestResponse> SendAsync(string method, string endpoint, IReadOnlyDictionary<string, object> multipartParams, CancellationToken cancelToken, bool headerOnly = false, string reason = null,
+            IEnumerable<KeyValuePair<string, IEnumerable<string>>> requestHeaders = null);
     }
 }

src/Discord.Net.Core/RequestOptions.cs

@@ -1,5 +1,6 @@
 using Discord.Net;
 using System;
+using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -19,7 +20,7 @@ namespace Discord
         ///     Gets or sets the maximum time to wait for this request to complete.
         /// </summary>
         /// <remarks>
-        ///     Gets or set the max time, in milliseconds, to wait for this request to complete. If 
+        ///     Gets or set the max time, in milliseconds, to wait for this request to complete. If
         ///     <c>null</c>, a request will not time out. If a rate limit has been triggered for this request's bucket
         ///     and will not be unpaused in time, this request will fail immediately.
         /// </remarks>
@@ -53,7 +54,7 @@ namespace Discord
 		/// </summary>
 		/// <remarks>
 		///		This property can also be set in <see cref="DiscordConfig"/>.
-		///		On a per-request basis, the system clock should only be disabled 
+		///		On a per-request basis, the system clock should only be disabled
 		///		when millisecond precision is especially important, and the
 		///		hosting system is known to have a desynced clock.
 		/// </remarks>
@@ -70,8 +71,10 @@ namespace Discord
         internal bool IsReactionBucket { get; set; }
         internal bool IsGatewayBucket { get; set; }
 
+        internal IDictionary<string, IEnumerable<string>> RequestHeaders { get; }
+
         internal static RequestOptions CreateOrClone(RequestOptions options)
-        {            
+        {
             if (options == null)
                 return new RequestOptions();
             else
@@ -96,8 +99,9 @@ namespace Discord
         public RequestOptions()
         {
             Timeout = DiscordConfig.DefaultRequestTimeout;
+            RequestHeaders = new Dictionary<string, IEnumerable<string>>();
         }
-        
+
         public RequestOptions Clone() => MemberwiseClone() as RequestOptions;
     }
 }

src/Discord.Net.Core/Utils/Preconditions.cs

@@ -55,7 +55,7 @@ namespace Discord
                 if (obj.Value == null) throw CreateNotNullException(name, msg);
                 if (obj.Value.Trim().Length == 0) throw CreateNotEmptyException(name, msg);
             }
-        }        
+        }
 
         private static ArgumentException CreateNotEmptyException(string name, string msg)
             => new ArgumentException(message: msg ?? "Argument cannot be blank.", paramName: name);
@@ -129,7 +129,7 @@ namespace Discord
 
         private static ArgumentException CreateNotEqualException<T>(string name, string msg, T value)
             => new ArgumentException(message: msg ?? $"Value may not be equal to {value}.", paramName: name);
-        
+
         /// <exception cref="ArgumentException">Value must be at least <paramref name="value"/>.</exception>
         public static void AtLeast(sbyte obj, sbyte value, string name, string msg = null) { if (obj < value) throw CreateAtLeastException(name, msg, value); }
         /// <exception cref="ArgumentException">Value must be at least <paramref name="value"/>.</exception>
@@ -165,7 +165,7 @@ namespace Discord
 
         private static ArgumentException CreateAtLeastException<T>(string name, string msg, T value)
             => new ArgumentException(message: msg ?? $"Value must be at least {value}.", paramName: name);
-        
+
         /// <exception cref="ArgumentException">Value must be greater than <paramref name="value"/>.</exception>
         public static void GreaterThan(sbyte obj, sbyte value, string name, string msg = null) { if (obj <= value) throw CreateGreaterThanException(name, msg, value); }
         /// <exception cref="ArgumentException">Value must be greater than <paramref name="value"/>.</exception>
@@ -201,7 +201,7 @@ namespace Discord
 
         private static ArgumentException CreateGreaterThanException<T>(string name, string msg, T value)
             => new ArgumentException(message: msg ?? $"Value must be greater than {value}.", paramName: name);
-        
+
         /// <exception cref="ArgumentException">Value must be at most <paramref name="value"/>.</exception>
         public static void AtMost(sbyte obj, sbyte value, string name, string msg = null) { if (obj > value) throw CreateAtMostException(name, msg, value); }
         /// <exception cref="ArgumentException">Value must be at most <paramref name="value"/>.</exception>
@@ -237,7 +237,7 @@ namespace Discord
 
         private static ArgumentException CreateAtMostException<T>(string name, string msg, T value)
             => new ArgumentException(message: msg ?? $"Value must be at most {value}.", paramName: name);
-        
+
         /// <exception cref="ArgumentException">Value must be less than <paramref name="value"/>.</exception>
         public static void LessThan(sbyte obj, sbyte value, string name, string msg = null) { if (obj >= value) throw CreateLessThanException(name, msg, value); }
         /// <exception cref="ArgumentException">Value must be less than <paramref name="value"/>.</exception>

src/Discord.Net.Interactions/InteractionService.cs

@@ -83,6 +83,11 @@ namespace Discord.Interactions
         public event Func<ModalCommandInfo, IInteractionContext, IResult, Task> ModalCommandExecuted { add { _modalCommandExecutedEvent.Add(value); } remove { _modalCommandExecutedEvent.Remove(value); } }
         internal readonly AsyncEvent<Func<ModalCommandInfo, IInteractionContext, IResult, Task>> _modalCommandExecutedEvent = new();
 
+        /// <summary>
+        ///     Get the <see cref="ILocalizationManager"/> used by this Interaction Service instance to localize strings.
+        /// </summary>
+        public ILocalizationManager LocalizationManager { get; set; }
+
         private readonly ConcurrentDictionary<Type, ModuleInfo> _typedModuleDefs;
         private readonly CommandMap<SlashCommandInfo> _slashCommandMap;
         private readonly ConcurrentDictionary<ApplicationCommandType, CommandMap<ContextCommandInfo>> _contextCommandMaps;
@@ -203,6 +208,7 @@ namespace Discord.Interactions
             _enableAutocompleteHandlers = config.EnableAutocompleteHandlers;
             _autoServiceScopes = config.AutoServiceScopes;
             _restResponseCallback = config.RestResponseCallback;
+            LocalizationManager = config.LocalizationManager;
 
             _typeConverterMap = new TypeMap<TypeConverter, IApplicationCommandInteractionDataOption>(this, new ConcurrentDictionary<Type, TypeConverter>
                 {

src/Discord.Net.Interactions/InteractionServiceConfig.cs

@@ -64,6 +64,11 @@ namespace Discord.Interactions
         ///     Gets or sets whether a command execution should exit when a modal command encounters a missing modal component value.
         /// </summary>
         public bool ExitOnMissingModalField { get; set; } = false;
+
+        /// <summary>
+        ///     Localization provider to be used when registering application commands.
+        /// </summary>
+        public ILocalizationManager LocalizationManager { get; set; }
     }
 
     /// <summary>

src/Discord.Net.Interactions/LocalizationManagers/ILocalizationManager.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace Discord.Interactions
+{
+    /// <summary>
+    ///     Respresents a localization provider for Discord Application Commands.
+    /// </summary>
+    public interface ILocalizationManager
+    {
+        /// <summary>
+        ///     Get every the resource name for every available locale.
+        /// </summary>
+        /// <param name="key">Location of the resource.</param>
+        /// <param name="destinationType">Type of the resource.</param>
+        /// <returns>
+        ///     A dictionary containing every available locale and the resource name.
+        /// </returns>
+        IDictionary<string, string> GetAllNames(IList<string> key, LocalizationTarget destinationType);
+
+        /// <summary>
+        ///     Get every the resource description for every available locale.
+        /// </summary>
+        /// <param name="key">Location of the resource.</param>
+        /// <param name="destinationType">Type of the resource.</param>
+        /// <returns>
+        ///     A dictionary containing every available locale and the resource name.
+        /// </returns>
+        IDictionary<string, string> GetAllDescriptions(IList<string> key, LocalizationTarget destinationType);
+    }
+}

src/Discord.Net.Interactions/LocalizationManagers/JsonLocalizationManager.cs

@@ -0,0 +1,72 @@
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+
+namespace Discord.Interactions
+{
+    /// <summary>
+    ///     The default localization provider for Json resource files.
+    /// </summary>
+    public sealed class JsonLocalizationManager : ILocalizationManager
+    {
+        private const string NameIdentifier = "name";
+        private const string DescriptionIdentifier = "description";
+        private const string SpaceToken = "~";
+
+        private readonly string _basePath;
+        private readonly string _fileName;
+        private readonly Regex _localeParserRegex = new Regex(@"\w+.(?<locale>\w{2}(?:-\w{2})?).json", RegexOptions.Compiled | RegexOptions.Singleline);
+
+        /// <summary>
+        ///     Initializes a new instance of the <see cref="JsonLocalizationManager"/> class.
+        /// </summary>
+        /// <param name="basePath">Base path of the Json file.</param>
+        /// <param name="fileName">Name of the Json file.</param>
+        public JsonLocalizationManager(string basePath, string fileName)
+        {
+            _basePath = basePath;
+            _fileName = fileName;
+        }
+
+        /// <inheritdoc />
+        public IDictionary<string, string> GetAllDescriptions(IList<string> key, LocalizationTarget destinationType) =>
+            GetValues(key, DescriptionIdentifier);
+
+        /// <inheritdoc />
+        public IDictionary<string, string> GetAllNames(IList<string> key, LocalizationTarget destinationType) =>
+            GetValues(key, NameIdentifier);
+
+        private string[] GetAllFiles() =>
+            Directory.GetFiles(_basePath, $"{_fileName}.*.json", SearchOption.TopDirectoryOnly);
+
+        private IDictionary<string, string> GetValues(IList<string> key, string identifier)
+        {
+            var result = new Dictionary<string, string>();
+            var files = GetAllFiles();
+
+            foreach (var file in files)
+            {
+                var match = _localeParserRegex.Match(Path.GetFileName(file));
+                if (!match.Success)
+                    continue;
+
+                var locale = match.Groups["locale"].Value;
+
+                using var sr = new StreamReader(file);
+                using var jr = new JsonTextReader(sr);
+                var obj = JObject.Load(jr);
+                var token = string.Join(".", key.Select(x => $"['{x}']")) + $".{identifier}";
+                var value = (string)obj.SelectToken(token);
+                if (value is not null)
+                    result[locale] = value;
+            }
+
+            return result;
+        }
+    }
+}

src/Discord.Net.Interactions/LocalizationManagers/ResxLocalizationManager.cs

@@ -0,0 +1,55 @@
+using System.Collections.Generic;
+using System.Globalization;
+using System.Reflection;
+using System.Resources;
+
+namespace Discord.Interactions
+{
+    /// <summary>
+    ///     The default localization provider for Resx files.
+    /// </summary>
+    public sealed class ResxLocalizationManager : ILocalizationManager
+    {
+        private const string NameIdentifier = "name";
+        private const string DescriptionIdentifier = "description";
+
+        private readonly ResourceManager _resourceManager;
+        private readonly IEnumerable<CultureInfo> _supportedLocales;
+
+        /// <summary>
+        ///     Initializes a new instance of the <see cref="ResxLocalizationManager"/> class.
+        /// </summary>
+        /// <param name="baseResource">Name of the base resource.</param>
+        /// <param name="assembly">The main assembly for the resources.</param>
+        /// <param name="supportedLocales">Cultures the <see cref="ResxLocalizationManager"/> should search for.</param>
+        public ResxLocalizationManager(string baseResource, Assembly assembly, params CultureInfo[] supportedLocales)
+        {
+            _supportedLocales = supportedLocales;
+            _resourceManager = new ResourceManager(baseResource, assembly);
+        }
+
+        /// <inheritdoc />
+        public IDictionary<string, string> GetAllDescriptions(IList<string> key, LocalizationTarget destinationType) =>
+            GetValues(key, DescriptionIdentifier);
+
+        /// <inheritdoc />
+        public IDictionary<string, string> GetAllNames(IList<string> key, LocalizationTarget destinationType) =>
+            GetValues(key, NameIdentifier);
+
+        private IDictionary<string, string> GetValues(IList<string> key, string identifier)
+        {
+            var entryKey = (string.Join(".", key) + "." + identifier);
+
+            var result = new Dictionary<string, string>();
+
+            foreach (var locale in _supportedLocales)
+            {
+                var value = _resourceManager.GetString(entryKey, locale);
+                if (value is not null)
+                    result[locale.Name] = value;
+            }
+
+            return result;
+        }
+    }
+}

src/Discord.Net.Interactions/LocalizationTarget.cs

@@ -0,0 +1,25 @@
+namespace Discord.Interactions
+{
+    /// <summary>
+    ///     Resource targets for localization.
+    /// </summary>
+    public enum LocalizationTarget
+    {
+        /// <summary>
+        ///     Target is a <see cref="IInteractionModuleBase"/> tagged with a <see cref="GroupAttribute"/>.
+        /// </summary>
+        Group,
+        /// <summary>
+        ///     Target is an application command method.
+        /// </summary>
+        Command,
+        /// <summary>
+        ///     Target is a Slash Command parameter.
+        /// </summary>
+        Parameter,
+        /// <summary>
+        ///     Target is a Slash Command parameter choice.
+        /// </summary>
+        Choice
+    }
+}

src/Discord.Net.Interactions/Map/CommandMap.cs

@@ -42,7 +42,7 @@ namespace Discord.Interactions
 
         public void RemoveCommand(T command)
         {
-            var key = ParseCommandName(command);
+            var key = CommandHierarchy.GetCommandPath(command);
 
             _root.RemoveCommand(key, 0);
         }
@@ -60,28 +60,9 @@ namespace Discord.Interactions
 
         private void AddCommand(T command)
         {
-            var key = ParseCommandName(command);
+            var key = CommandHierarchy.GetCommandPath(command);
 
             _root.AddCommand(key, 0, command);
         }
-
-        private IList<string> ParseCommandName(T command)
-        {
-            var keywords = new List<string>() { command.Name };
-
-            var currentParent = command.Module;
-
-            while (currentParent != null)
-            {
-                if (!string.IsNullOrEmpty(currentParent.SlashGroupName))
-                    keywords.Add(currentParent.SlashGroupName);
-
-                currentParent = currentParent.Parent;
-            }
-
-            keywords.Reverse();
-
-            return keywords;
-        }
     }
 }

src/Discord.Net.Interactions/Utilities/ApplicationCommandRestUtil.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
 
 namespace Discord.Interactions
@@ -9,6 +10,9 @@ namespace Discord.Interactions
         #region Parameters
         public static ApplicationCommandOptionProperties ToApplicationCommandOptionProps(this SlashCommandParameterInfo parameterInfo)
         {
+            var localizationManager = parameterInfo.Command.Module.CommandService.LocalizationManager;
+            var parameterPath = parameterInfo.GetParameterPath();
+
             var props = new ApplicationCommandOptionProperties
             {
                 Name = parameterInfo.Name,
@@ -18,12 +22,15 @@ namespace Discord.Interactions
                 Choices = parameterInfo.Choices?.Select(x => new ApplicationCommandOptionChoiceProperties
                 {
                     Name = x.Name,
-                    Value = x.Value
+                    Value = x.Value,
+                    NameLocalizations = localizationManager?.GetAllNames(parameterInfo.GetChoicePath(x), LocalizationTarget.Choice) ?? ImmutableDictionary<string, string>.Empty
                 })?.ToList(),
                 ChannelTypes = parameterInfo.ChannelTypes?.ToList(),
                 IsAutocomplete = parameterInfo.IsAutocomplete,
                 MaxValue = parameterInfo.MaxValue,
                 MinValue = parameterInfo.MinValue,
+                NameLocalizations = localizationManager?.GetAllNames(parameterPath, LocalizationTarget.Parameter) ?? ImmutableDictionary<string, string>.Empty,
+                DescriptionLocalizations = localizationManager?.GetAllDescriptions(parameterPath, LocalizationTarget.Parameter) ?? ImmutableDictionary<string, string>.Empty,
                 MinLength = parameterInfo.MinLength,
                 MaxLength = parameterInfo.MaxLength,
             };
@@ -38,13 +45,19 @@ namespace Discord.Interactions
 
         public static SlashCommandProperties ToApplicationCommandProps(this SlashCommandInfo commandInfo)
         {
+            var commandPath = commandInfo.GetCommandPath();
+            var localizationManager = commandInfo.Module.CommandService.LocalizationManager;
+
             var props = new SlashCommandBuilder()
             {
                 Name = commandInfo.Name,
                 Description = commandInfo.Description,
+                IsDefaultPermission = commandInfo.DefaultPermission,
                 IsDMEnabled = commandInfo.IsEnabledInDm,
                 DefaultMemberPermissions = ((commandInfo.DefaultMemberPermissions ?? 0) | (commandInfo.Module.DefaultMemberPermissions ?? 0)).SanitizeGuildPermissions(),
-            }.Build();
+            }.WithNameLocalizations(localizationManager?.GetAllNames(commandPath, LocalizationTarget.Command) ?? ImmutableDictionary<string, string>.Empty)
+            .WithDescriptionLocalizations(localizationManager?.GetAllDescriptions(commandPath, LocalizationTarget.Command) ?? ImmutableDictionary<string, string>.Empty)
+            .Build();
 
             if (commandInfo.Parameters.Count > SlashCommandBuilder.MaxOptionsCount)
                 throw new InvalidOperationException($"Slash Commands cannot have more than {SlashCommandBuilder.MaxOptionsCount} command parameters");
@@ -54,18 +67,30 @@ namespace Discord.Interactions
             return props;
         }
 
-        public static ApplicationCommandOptionProperties ToApplicationCommandOptionProps(this SlashCommandInfo commandInfo) =>
-            new ApplicationCommandOptionProperties
+        public static ApplicationCommandOptionProperties ToApplicationCommandOptionProps(this SlashCommandInfo commandInfo)
+        {
+            var localizationManager = commandInfo.Module.CommandService.LocalizationManager;
+            var commandPath = commandInfo.GetCommandPath();
+
+            return new ApplicationCommandOptionProperties
             {
                 Name = commandInfo.Name,
                 Description = commandInfo.Description,
                 Type = ApplicationCommandOptionType.SubCommand,
                 IsRequired = false,
-                Options = commandInfo.FlattenedParameters?.Select(x => x.ToApplicationCommandOptionProps())?.ToList()
+                Options = commandInfo.FlattenedParameters?.Select(x => x.ToApplicationCommandOptionProps())
+                    ?.ToList(),
+                NameLocalizations = localizationManager?.GetAllNames(commandPath, LocalizationTarget.Command) ?? ImmutableDictionary<string, string>.Empty,
+                DescriptionLocalizations = localizationManager?.GetAllDescriptions(commandPath, LocalizationTarget.Command) ?? ImmutableDictionary<string, string>.Empty
             };
+        }
 
         public static ApplicationCommandProperties ToApplicationCommandProps(this ContextCommandInfo commandInfo)
-            => commandInfo.CommandType switch
+        {
+            var localizationManager = commandInfo.Module.CommandService.LocalizationManager;
+            var commandPath = commandInfo.GetCommandPath();
+
+            return commandInfo.CommandType switch
             {
                 ApplicationCommandType.Message => new MessageCommandBuilder
                 {
@@ -73,16 +98,21 @@ namespace Discord.Interactions
                     IsDefaultPermission = commandInfo.DefaultPermission,
                     DefaultMemberPermissions = ((commandInfo.DefaultMemberPermissions ?? 0) | (commandInfo.Module.DefaultMemberPermissions ?? 0)).SanitizeGuildPermissions(),
                     IsDMEnabled = commandInfo.IsEnabledInDm
-                }.Build(),
+                }
+                .WithNameLocalizations(localizationManager?.GetAllNames(commandPath, LocalizationTarget.Command) ?? ImmutableDictionary<string, string>.Empty)
+                .Build(),
                 ApplicationCommandType.User => new UserCommandBuilder
                 {
                     Name = commandInfo.Name,
                     IsDefaultPermission = commandInfo.DefaultPermission,
                     DefaultMemberPermissions = ((commandInfo.DefaultMemberPermissions ?? 0) | (commandInfo.Module.DefaultMemberPermissions ?? 0)).SanitizeGuildPermissions(),
                     IsDMEnabled = commandInfo.IsEnabledInDm
-                }.Build(),
+                }
+                .WithNameLocalizations(localizationManager?.GetAllNames(commandPath, LocalizationTarget.Command) ?? ImmutableDictionary<string, string>.Empty)
+                .Build(),
                 _ => throw new InvalidOperationException($"{commandInfo.CommandType} isn't a supported command type.")
             };
+        }
         #endregion
 
         #region Modules
@@ -123,6 +153,9 @@ namespace Discord.Interactions
 
                 options.AddRange(moduleInfo.SubModules?.SelectMany(x => x.ParseSubModule(args, ignoreDontRegister)));
 
+                var localizationManager = moduleInfo.CommandService.LocalizationManager;
+                var modulePath = moduleInfo.GetModulePath();
+
                 var props = new SlashCommandBuilder
                 {
                     Name = moduleInfo.SlashGroupName,
@@ -130,7 +163,10 @@ namespace Discord.Interactions
                     IsDefaultPermission = moduleInfo.DefaultPermission,
                     IsDMEnabled = moduleInfo.IsEnabledInDm,
                     DefaultMemberPermissions = moduleInfo.DefaultMemberPermissions
-                }.Build();
+                }
+                .WithNameLocalizations(localizationManager?.GetAllNames(modulePath, LocalizationTarget.Group) ?? ImmutableDictionary<string, string>.Empty)
+                .WithDescriptionLocalizations(localizationManager?.GetAllDescriptions(modulePath, LocalizationTarget.Group) ?? ImmutableDictionary<string, string>.Empty)
+                .Build();
 
                 if (options.Count > SlashCommandBuilder.MaxOptionsCount)
                     throw new InvalidOperationException($"Slash Commands cannot have more than {SlashCommandBuilder.MaxOptionsCount} command parameters");
@@ -168,7 +204,11 @@ namespace Discord.Interactions
                     Name = moduleInfo.SlashGroupName,
                     Description = moduleInfo.Description,
                     Type = ApplicationCommandOptionType.SubCommandGroup,
-                    Options = options
+                    Options = options,
+                    NameLocalizations = moduleInfo.CommandService.LocalizationManager?.GetAllNames(moduleInfo.GetModulePath(), LocalizationTarget.Group)
+                        ?? ImmutableDictionary<string, string>.Empty,
+                    DescriptionLocalizations = moduleInfo.CommandService.LocalizationManager?.GetAllDescriptions(moduleInfo.GetModulePath(), LocalizationTarget.Group)
+                        ?? ImmutableDictionary<string, string>.Empty,
                 } };
         }
 
@@ -183,17 +223,29 @@ namespace Discord.Interactions
                     Name = command.Name,
                     Description = command.Description,
                     IsDefaultPermission = command.IsDefaultPermission,
-                    Options = command.Options?.Select(x => x.ToApplicationCommandOptionProps())?.ToList() ?? Optional<List<ApplicationCommandOptionProperties>>.Unspecified
+                    DefaultMemberPermissions = (GuildPermission)command.DefaultMemberPermissions.RawValue,
+                    IsDMEnabled = command.IsEnabledInDm,
+                    Options = command.Options?.Select(x => x.ToApplicationCommandOptionProps())?.ToList() ?? Optional<List<ApplicationCommandOptionProperties>>.Unspecified,
+                    NameLocalizations = command.NameLocalizations?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty,
+                    DescriptionLocalizations = command.DescriptionLocalizations?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty,
                 },
                 ApplicationCommandType.User => new UserCommandProperties
                 {
                     Name = command.Name,
-                    IsDefaultPermission = command.IsDefaultPermission
+                    IsDefaultPermission = command.IsDefaultPermission,
+                    DefaultMemberPermissions = (GuildPermission)command.DefaultMemberPermissions.RawValue,
+                    IsDMEnabled = command.IsEnabledInDm,
+                    NameLocalizations = command.NameLocalizations?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty,
+                    DescriptionLocalizations = command.DescriptionLocalizations?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty
                 },
                 ApplicationCommandType.Message => new MessageCommandProperties
                 {
                     Name = command.Name,
-                    IsDefaultPermission = command.IsDefaultPermission
+                    IsDefaultPermission = command.IsDefaultPermission,
+                    DefaultMemberPermissions = (GuildPermission)command.DefaultMemberPermissions.RawValue,
+                    IsDMEnabled = command.IsEnabledInDm,
+                    NameLocalizations = command.NameLocalizations?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty,
+                    DescriptionLocalizations = command.DescriptionLocalizations?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty
                 },
                 _ => throw new InvalidOperationException($"Cannot create command properties for command type {command.Type}"),
             };
@@ -206,18 +258,20 @@ namespace Discord.Interactions
                 Description = commandOption.Description,
                 Type = commandOption.Type,
                 IsRequired = commandOption.IsRequired,
+                ChannelTypes = commandOption.ChannelTypes?.ToList(),
+                IsAutocomplete = commandOption.IsAutocomplete.GetValueOrDefault(),
+                MinValue = commandOption.MinValue,
+                MaxValue = commandOption.MaxValue,
                 Choices = commandOption.Choices?.Select(x => new ApplicationCommandOptionChoiceProperties
                 {
                     Name = x.Name,
                     Value = x.Value
                 }).ToList(),
                 Options = commandOption.Options?.Select(x => x.ToApplicationCommandOptionProps()).ToList(),
+                NameLocalizations = commandOption.NameLocalizations?.ToImmutableDictionary(),
+                DescriptionLocalizations = commandOption.DescriptionLocalizations?.ToImmutableDictionary(),
                 MaxLength = commandOption.MaxLength,
                 MinLength = commandOption.MinLength,
-                MaxValue = commandOption.MaxValue,
-                MinValue = commandOption.MinValue,
-                IsAutocomplete = commandOption.IsAutocomplete.GetValueOrDefault(),
-                ChannelTypes = commandOption.ChannelTypes.ToList(),
             };
 
         public static Modal ToModal(this ModalInfo modalInfo, string customId, Action<ModalBuilder> modifyModal = null)

src/Discord.Net.Interactions/Utilities/CommandHierarchy.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+
+namespace Discord.Interactions
+{
+    internal static class CommandHierarchy
+    {
+        public const char EscapeChar = '$';
+
+        public static IList<string> GetModulePath(this ModuleInfo moduleInfo)
+        {
+            var result = new List<string>();
+
+            var current = moduleInfo;
+            while (current is not null)
+            {
+                if (current.IsSlashGroup)
+                    result.Insert(0, current.SlashGroupName);
+
+                current = current.Parent;
+            }
+
+            return result;
+        }
+
+        public static IList<string> GetCommandPath(this ICommandInfo commandInfo)
+        {
+            if (commandInfo.IgnoreGroupNames)
+                return new string[] { commandInfo.Name };
+
+            var path = commandInfo.Module.GetModulePath();
+            path.Add(commandInfo.Name);
+            return path;
+        }
+
+        public static IList<string> GetParameterPath(this IParameterInfo parameterInfo)
+        {
+            var path = parameterInfo.Command.GetCommandPath();
+            path.Add(parameterInfo.Name);
+            return path;
+        }
+
+        public static IList<string> GetChoicePath(this IParameterInfo parameterInfo, ParameterChoice choice)
+        {
+            var path = parameterInfo.GetParameterPath();
+            path.Add(choice.Name);
+            return path;
+        }
+
+        public static IList<string> GetTypePath(Type type) =>
+            new string[] { EscapeChar + type.FullName };
+    }
+}

src/Discord.Net.Rest/API/Common/ApplicationCommand.cs

@@ -1,4 +1,5 @@
 using Newtonsoft.Json;
+using System.Collections.Generic;
 
 namespace Discord.API
 {
@@ -25,6 +26,18 @@ namespace Discord.API
         [JsonProperty("default_permission")]
         public Optional<bool> DefaultPermissions { get; set; }
 
+        [JsonProperty("name_localizations")]
+        public Optional<Dictionary<string, string>> NameLocalizations { get; set; }
+
+        [JsonProperty("description_localizations")]
+        public Optional<Dictionary<string, string>> DescriptionLocalizations { get; set; }
+
+        [JsonProperty("name_localized")]
+        public Optional<string> NameLocalized { get; set; }
+
+        [JsonProperty("description_localized")]
+        public Optional<string> DescriptionLocalized { get; set; }
+        
         // V2 Permissions
         [JsonProperty("dm_permission")]
         public Optional<bool?> DmPermission { get; set; }

src/Discord.Net.Rest/API/Common/ApplicationCommandOption.cs

@@ -1,4 +1,5 @@
 using Newtonsoft.Json;
+using System.Collections.Generic;
 using System.Linq;
 
 namespace Discord.API
@@ -38,6 +39,18 @@ namespace Discord.API
         [JsonProperty("channel_types")]
         public Optional<ChannelType[]> ChannelTypes { get; set; }
 
+        [JsonProperty("name_localizations")]
+        public Optional<Dictionary<string, string>> NameLocalizations { get; set; }
+
+        [JsonProperty("description_localizations")]
+        public Optional<Dictionary<string, string>> DescriptionLocalizations { get; set; }
+
+        [JsonProperty("name_localized")]
+        public Optional<string> NameLocalized { get; set; }
+
+        [JsonProperty("description_localized")]
+        public Optional<string> DescriptionLocalized { get; set; }
+
         [JsonProperty("min_length")]
         public Optional<int> MinLength { get; set; }
 
@@ -69,6 +82,11 @@ namespace Discord.API
             Name = cmd.Name;
             Type = cmd.Type;
             Description = cmd.Description;
+
+            NameLocalizations = cmd.NameLocalizations?.ToDictionary() ?? Optional<Dictionary<string, string>>.Unspecified;
+            DescriptionLocalizations = cmd.DescriptionLocalizations?.ToDictionary() ?? Optional<Dictionary<string, string>>.Unspecified;
+            NameLocalized = cmd.NameLocalized;
+            DescriptionLocalized = cmd.DescriptionLocalized;
         }
         public ApplicationCommandOption(ApplicationCommandOptionProperties option)
         {
@@ -94,6 +112,9 @@ namespace Discord.API
             Type = option.Type;
             Description = option.Description;
             Autocomplete = option.IsAutocomplete;
+
+            NameLocalizations = option.NameLocalizations?.ToDictionary() ?? Optional<Dictionary<string, string>>.Unspecified;
+            DescriptionLocalizations = option.DescriptionLocalizations?.ToDictionary() ?? Optional<Dictionary<string, string>>.Unspecified;
         }
     }
 }

src/Discord.Net.Rest/API/Common/ApplicationCommandOptionChoice.cs

@@ -1,4 +1,5 @@
 using Newtonsoft.Json;
+using System.Collections.Generic;
 
 namespace Discord.API
 {
@@ -9,5 +10,11 @@ namespace Discord.API
 
         [JsonProperty("value")]
         public object Value { get; set; }
+
+        [JsonProperty("name_localizations")]
+        public Optional<Dictionary<string, string>> NameLocalizations { get; set; }
+
+        [JsonProperty("name_localized")]
+        public Optional<string> NameLocalized { get; set; }
     }
 }

src/Discord.Net.Rest/API/Rest/CreateApplicationCommandParams.cs

@@ -1,4 +1,8 @@
 using Newtonsoft.Json;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
 
 namespace Discord.API.Rest
 {
@@ -19,6 +23,12 @@ namespace Discord.API.Rest
         [JsonProperty("default_permission")]
         public Optional<bool> DefaultPermission { get; set; }
 
+        [JsonProperty("name_localizations")]
+        public Optional<Dictionary<string, string>> NameLocalizations { get; set; }
+
+        [JsonProperty("description_localizations")]
+        public Optional<Dictionary<string, string>> DescriptionLocalizations { get; set; }
+
         [JsonProperty("dm_permission")]
         public Optional<bool?> DmPermission { get; set; }
 
@@ -26,12 +36,15 @@ namespace Discord.API.Rest
         public Optional<GuildPermission?> DefaultMemberPermission { get; set; }
 
         public CreateApplicationCommandParams() { }
-        public CreateApplicationCommandParams(string name, string description, ApplicationCommandType type, ApplicationCommandOption[] options = null)
+        public CreateApplicationCommandParams(string name, string description, ApplicationCommandType type, ApplicationCommandOption[] options = null,
+            IDictionary<string, string> nameLocalizations = null, IDictionary<string, string> descriptionLocalizations = null)
         {
             Name = name;
             Description = description;
             Options = Optional.Create(options);
             Type = type;
+            NameLocalizations = nameLocalizations?.ToDictionary(x => x.Key, x => x.Value) ?? Optional<Dictionary<string, string>>.Unspecified;
+            DescriptionLocalizations = descriptionLocalizations?.ToDictionary(x => x.Key, x => x.Value) ?? Optional<Dictionary<string, string>>.Unspecified;
         }
     }
 }

src/Discord.Net.Rest/API/Rest/ModifyApplicationCommandParams.cs

@@ -1,4 +1,5 @@
 using Newtonsoft.Json;
+using System.Collections.Generic;
 
 namespace Discord.API.Rest
 {
@@ -15,5 +16,11 @@ namespace Discord.API.Rest
 
         [JsonProperty("default_permission")]
         public Optional<bool> DefaultPermission { get; set; }
+
+        [JsonProperty("name_localizations")]
+        public Optional<Dictionary<string, string>> NameLocalizations { get; set; }
+
+        [JsonProperty("description_localizations")]
+        public Optional<Dictionary<string, string>> DescriptionLocalizations { get; set; }
     }
 }

src/Discord.Net.Rest/BaseDiscordClient.cs

@@ -243,7 +243,7 @@ namespace Discord.Rest
             => Task.FromResult<IApplicationCommand>(null);
 
         /// <inheritdoc />
-        Task<IReadOnlyCollection<IApplicationCommand>> IDiscordClient.GetGlobalApplicationCommandsAsync(RequestOptions options)
+        Task<IReadOnlyCollection<IApplicationCommand>> IDiscordClient.GetGlobalApplicationCommandsAsync(bool withLocalizations, string locale, RequestOptions options)
             => Task.FromResult<IReadOnlyCollection<IApplicationCommand>>(ImmutableArray.Create<IApplicationCommand>());
         Task<IApplicationCommand> IDiscordClient.CreateGlobalApplicationCommand(ApplicationCommandProperties properties, RequestOptions options)
             => Task.FromResult<IApplicationCommand>(null);

src/Discord.Net.Rest/ClientHelper.cs

@@ -194,10 +194,10 @@ namespace Discord.Rest
             };
         }
 
-        public static async Task<IReadOnlyCollection<RestGlobalCommand>> GetGlobalApplicationCommandsAsync(BaseDiscordClient client,
-            RequestOptions options = null)
+        public static async Task<IReadOnlyCollection<RestGlobalCommand>> GetGlobalApplicationCommandsAsync(BaseDiscordClient client, bool withLocalizations = false,
+            string locale = null, RequestOptions options = null)
         {
-            var response = await client.ApiClient.GetGlobalApplicationCommandsAsync(options).ConfigureAwait(false);
+            var response = await client.ApiClient.GetGlobalApplicationCommandsAsync(withLocalizations, locale, options).ConfigureAwait(false);
 
             if (!response.Any())
                 return Array.Empty<RestGlobalCommand>();
@@ -212,10 +212,10 @@ namespace Discord.Rest
             return model != null ? RestGlobalCommand.Create(client, model) : null;
         }
 
-        public static async Task<IReadOnlyCollection<RestGuildCommand>> GetGuildApplicationCommandsAsync(BaseDiscordClient client, ulong guildId,
-            RequestOptions options = null)
+        public static async Task<IReadOnlyCollection<RestGuildCommand>> GetGuildApplicationCommandsAsync(BaseDiscordClient client, ulong guildId, bool withLocalizations = false,
+            string locale = null, RequestOptions options = null)
         {
-            var response = await client.ApiClient.GetGuildApplicationCommandsAsync(guildId, options).ConfigureAwait(false);
+            var response = await client.ApiClient.GetGuildApplicationCommandsAsync(guildId, withLocalizations, locale, options).ConfigureAwait(false);
 
             if (!response.Any())
                 return ImmutableArray.Create<RestGuildCommand>();

src/Discord.Net.Rest/DiscordRestApiClient.cs

@@ -8,6 +8,7 @@ using Newtonsoft.Json;
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
+using System.ComponentModel.Design;
 using System.Diagnostics;
 using System.Globalization;
 using System.IO;
@@ -1212,11 +1213,22 @@ namespace Discord.API
         #endregion
 
         #region Interactions
-        public async Task<ApplicationCommand[]> GetGlobalApplicationCommandsAsync(RequestOptions options = null)
+        public async Task<ApplicationCommand[]> GetGlobalApplicationCommandsAsync(bool withLocalizations = false, string locale = null, RequestOptions options = null)
         {
             options = RequestOptions.CreateOrClone(options);
 
-            return await SendAsync<ApplicationCommand[]>("GET", () => $"applications/{CurrentApplicationId}/commands", new BucketIds(), options: options).ConfigureAwait(false);
+            if (locale is not null)
+            {
+                if (!System.Text.RegularExpressions.Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                    throw new ArgumentException($"{locale} is not a valid locale.", nameof(locale));
+
+                options.RequestHeaders["X-Discord-Locale"] = new[] { locale };
+            }
+
+            //with_localizations=false doesnt return localized names and descriptions
+            var query = withLocalizations ? "?with_localizations=true" : string.Empty;
+            return await SendAsync<ApplicationCommand[]>("GET", () => $"applications/{CurrentApplicationId}/commands{query}",
+                new BucketIds(), options: options).ConfigureAwait(false);
         }
 
         public async Task<ApplicationCommand> GetGlobalApplicationCommandAsync(ulong id, RequestOptions options = null)
@@ -1281,13 +1293,24 @@ namespace Discord.API
             return await SendJsonAsync<ApplicationCommand[]>("PUT", () => $"applications/{CurrentApplicationId}/commands", commands, new BucketIds(), options: options).ConfigureAwait(false);
         }
 
-        public async Task<ApplicationCommand[]> GetGuildApplicationCommandsAsync(ulong guildId, RequestOptions options = null)
+        public async Task<ApplicationCommand[]> GetGuildApplicationCommandsAsync(ulong guildId, bool withLocalizations = false, string locale = null, RequestOptions options = null)
         {
             options = RequestOptions.CreateOrClone(options);
 
             var bucket = new BucketIds(guildId: guildId);
 
-            return await SendAsync<ApplicationCommand[]>("GET", () => $"applications/{CurrentApplicationId}/guilds/{guildId}/commands", bucket, options: options).ConfigureAwait(false);
+            if (locale is not null)
+            {
+                if (!System.Text.RegularExpressions.Regex.IsMatch(locale, @"^\w{2}(?:-\w{2})?$"))
+                    throw new ArgumentException($"{locale} is not a valid locale.", nameof(locale));
+
+                options.RequestHeaders["X-Discord-Locale"] = new[] { locale };
+            }
+
+            //with_localizations=false doesnt return localized names and descriptions
+            var query = withLocalizations ? "?with_localizations=true" : string.Empty;
+            return await SendAsync<ApplicationCommand[]>("GET", () => $"applications/{CurrentApplicationId}/guilds/{guildId}/commands{query}",
+                bucket, options: options).ConfigureAwait(false);
         }
 
         public async Task<ApplicationCommand> GetGuildApplicationCommandAsync(ulong guildId, ulong commandId, RequestOptions options = null)

src/Discord.Net.Rest/DiscordRestClient.cs

@@ -25,7 +25,7 @@ namespace Discord.Rest
         ///     Gets the logged-in user.
         /// </summary>
         public new RestSelfUser CurrentUser { get => base.CurrentUser as RestSelfUser; internal set => base.CurrentUser = value; }
-        
+
         /// <inheritdoc />
         public DiscordRestClient() : this(new DiscordRestConfig()) { }
         /// <summary>
@@ -205,10 +205,10 @@ namespace Discord.Rest
             => ClientHelper.CreateGlobalApplicationCommandAsync(this, properties, options);
         public Task<RestGuildCommand> CreateGuildCommand(ApplicationCommandProperties properties, ulong guildId, RequestOptions options = null)
             => ClientHelper.CreateGuildApplicationCommandAsync(this, guildId, properties, options);
-        public Task<IReadOnlyCollection<RestGlobalCommand>> GetGlobalApplicationCommands(RequestOptions options = null)
-            => ClientHelper.GetGlobalApplicationCommandsAsync(this, options);
-        public Task<IReadOnlyCollection<RestGuildCommand>> GetGuildApplicationCommands(ulong guildId, RequestOptions options = null)
-            => ClientHelper.GetGuildApplicationCommandsAsync(this, guildId, options);
+        public Task<IReadOnlyCollection<RestGlobalCommand>> GetGlobalApplicationCommands(bool withLocalizations = false, string locale = null, RequestOptions options = null)
+            => ClientHelper.GetGlobalApplicationCommandsAsync(this, withLocalizations, locale, options);
+        public Task<IReadOnlyCollection<RestGuildCommand>> GetGuildApplicationCommands(ulong guildId, bool withLocalizations = false, string locale = null, RequestOptions options = null)
+            => ClientHelper.GetGuildApplicationCommandsAsync(this, guildId, withLocalizations, locale, options);
         public Task<IReadOnlyCollection<RestGlobalCommand>> BulkOverwriteGlobalCommands(ApplicationCommandProperties[] commandProperties, RequestOptions options = null)
             => ClientHelper.BulkOverwriteGlobalApplicationCommandAsync(this, commandProperties, options);
         public Task<IReadOnlyCollection<RestGuildCommand>> BulkOverwriteGuildCommands(ApplicationCommandProperties[] commandProperties, ulong guildId, RequestOptions options = null)
@@ -319,8 +319,8 @@ namespace Discord.Rest
             => await GetWebhookAsync(id, options).ConfigureAwait(false);
 
         /// <inheritdoc />
-        async Task<IReadOnlyCollection<IApplicationCommand>> IDiscordClient.GetGlobalApplicationCommandsAsync(RequestOptions options)
-            => await GetGlobalApplicationCommands(options).ConfigureAwait(false);
+        async Task<IReadOnlyCollection<IApplicationCommand>> IDiscordClient.GetGlobalApplicationCommandsAsync(bool withLocalizations, string locale, RequestOptions options)
+            => await GetGlobalApplicationCommands(withLocalizations, locale, options).ConfigureAwait(false);
         /// <inheritdoc />
         async Task<IApplicationCommand> IDiscordClient.GetGlobalApplicationCommandAsync(ulong id, RequestOptions options)
             => await ClientHelper.GetGlobalApplicationCommandAsync(this, id, options).ConfigureAwait(false);

src/Discord.Net.Rest/Entities/Guilds/GuildHelper.cs

@@ -362,10 +362,10 @@ namespace Discord.Rest
         #endregion
 
         #region Interactions
-        public static async Task<IReadOnlyCollection<RestGuildCommand>> GetSlashCommandsAsync(IGuild guild, BaseDiscordClient client,
-            RequestOptions options)
+        public static async Task<IReadOnlyCollection<RestGuildCommand>> GetSlashCommandsAsync(IGuild guild, BaseDiscordClient client, bool withLocalizations,
+            string locale, RequestOptions options)
         {
-            var models = await client.ApiClient.GetGuildApplicationCommandsAsync(guild.Id, options);
+            var models = await client.ApiClient.GetGuildApplicationCommandsAsync(guild.Id, withLocalizations, locale, options);
             return models.Select(x => RestGuildCommand.Create(client, x, guild.Id)).ToImmutableArray();
         }
         public static async Task<RestGuildCommand> GetSlashCommandAsync(IGuild guild, ulong id, BaseDiscordClient client,

src/Discord.Net.Rest/Entities/Guilds/RestGuild.cs

@@ -311,13 +311,15 @@ namespace Discord.Rest
         /// <summary>
         ///     Gets a collection of slash commands created by the current user in this guild.
         /// </summary>
+        /// <param name="withLocalizations">Whether to include full localization dictionaries in the returned objects, instead of the name localized and description localized fields.</param>
+        /// <param name="locale">The target locale of the localized name and description fields. Sets <c>X-Discord-Locale</c> header, which takes precedence over <c>Accept-Language</c>.</param>
         /// <param name="options">The options to be used when sending the request.</param>
         /// <returns>
         ///     A task that represents the asynchronous get operation. The task result contains a read-only collection of
         ///     slash commands created by the current user.
         /// </returns>
-        public Task<IReadOnlyCollection<RestGuildCommand>> GetSlashCommandsAsync(RequestOptions options = null)
-            => GuildHelper.GetSlashCommandsAsync(this, Discord, options);
+        public Task<IReadOnlyCollection<RestGuildCommand>> GetSlashCommandsAsync(bool withLocalizations = false, string locale = null, RequestOptions options = null)
+            => GuildHelper.GetSlashCommandsAsync(this, Discord, withLocalizations, locale, options);
 
         /// <summary>
         ///     Gets a slash command in the current guild.
@@ -928,13 +930,15 @@ namespace Discord.Rest
         /// <summary>
         ///     Gets this guilds slash commands
         /// </summary>
+        /// <param name="withLocalizations">Whether to include full localization dictionaries in the returned objects, instead of the name localized and description localized fields.</param>
+        /// <param name="locale">The target locale of the localized name and description fields. Sets <c>X-Discord-Locale</c> header, which takes precedence over <c>Accept-Language</c>.</param>
         /// <param name="options">The options to be used when sending the request.</param>
         /// <returns>
         ///     A task that represents the asynchronous get operation. The task result contains a read-only collection
         ///     of application commands found within the guild.
         /// </returns>
-        public async Task<IReadOnlyCollection<RestGuildCommand>> GetApplicationCommandsAsync (RequestOptions options = null)
-            => await ClientHelper.GetGuildApplicationCommandsAsync(Discord, Id, options).ConfigureAwait(false);
+        public async Task<IReadOnlyCollection<RestGuildCommand>> GetApplicationCommandsAsync (bool withLocalizations = false, string locale = null, RequestOptions options = null)
+            => await ClientHelper.GetGuildApplicationCommandsAsync(Discord, Id, withLocalizations, locale, options).ConfigureAwait(false);
         /// <summary>
         ///     Gets an application command within this guild with the specified id.
         /// </summary>
@@ -1467,8 +1471,8 @@ namespace Discord.Rest
         async Task<IReadOnlyCollection<IWebhook>> IGuild.GetWebhooksAsync(RequestOptions options)
             => await GetWebhooksAsync(options).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IReadOnlyCollection<IApplicationCommand>> IGuild.GetApplicationCommandsAsync (RequestOptions options)
-            => await GetApplicationCommandsAsync(options).ConfigureAwait(false);
+        async Task<IReadOnlyCollection<IApplicationCommand>> IGuild.GetApplicationCommandsAsync (bool withLocalizations, string locale, RequestOptions options)
+            => await GetApplicationCommandsAsync(withLocalizations, locale, options).ConfigureAwait(false);
         /// <inheritdoc />
         async Task<ICustomSticker> IGuild.CreateStickerAsync(string name, string description, IEnumerable<string> tags, Image image, RequestOptions options)
             => await CreateStickerAsync(name, description, tags, image, options);

src/Discord.Net.Rest/Entities/Interactions/InteractionHelper.cs

@@ -3,6 +3,7 @@ using Discord.API.Rest;
 using Discord.Net;
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
 using System.Net;
 using System.Threading.Tasks;
@@ -101,11 +102,12 @@ namespace Discord.Rest
                 DefaultPermission = arg.IsDefaultPermission.IsSpecified
                         ? arg.IsDefaultPermission.Value
                         : Optional<bool>.Unspecified,
+                NameLocalizations = arg.NameLocalizations?.ToDictionary(),
+                DescriptionLocalizations = arg.DescriptionLocalizations?.ToDictionary(),
 
                 // TODO: better conversion to nullable optionals
                 DefaultMemberPermission = arg.DefaultMemberPermissions.ToNullable(),
                 DmPermission = arg.IsDMEnabled.ToNullable() 
-                
             };
 
             if (arg is SlashCommandProperties slashProps)
@@ -140,12 +142,16 @@ namespace Discord.Rest
                     DefaultPermission = arg.IsDefaultPermission.IsSpecified
                         ? arg.IsDefaultPermission.Value
                         : Optional<bool>.Unspecified,
+                    NameLocalizations = arg.NameLocalizations?.ToDictionary(),
+                    DescriptionLocalizations = arg.DescriptionLocalizations?.ToDictionary(),
 
                     // TODO: better conversion to nullable optionals
                     DefaultMemberPermission = arg.DefaultMemberPermissions.ToNullable(),
                     DmPermission = arg.IsDMEnabled.ToNullable()
                 };
 
+                Console.WriteLine("Locales:" + string.Join(",", arg.NameLocalizations.Keys));
+
                 if (arg is SlashCommandProperties slashProps)
                 {
                     Preconditions.NotNullOrEmpty(slashProps.Description, nameof(slashProps.Description));
@@ -181,6 +187,8 @@ namespace Discord.Rest
                     DefaultPermission = arg.IsDefaultPermission.IsSpecified
                         ? arg.IsDefaultPermission.Value
                         : Optional<bool>.Unspecified,
+                    NameLocalizations = arg.NameLocalizations?.ToDictionary(),
+                    DescriptionLocalizations = arg.DescriptionLocalizations?.ToDictionary(),
 
                     // TODO: better conversion to nullable optionals
                     DefaultMemberPermission = arg.DefaultMemberPermissions.ToNullable(),
@@ -244,7 +252,9 @@ namespace Discord.Rest
                 Name = args.Name,
                 DefaultPermission = args.IsDefaultPermission.IsSpecified
                         ? args.IsDefaultPermission.Value
-                        : Optional<bool>.Unspecified
+                        : Optional<bool>.Unspecified,
+                NameLocalizations = args.NameLocalizations?.ToDictionary(),
+                DescriptionLocalizations = args.DescriptionLocalizations?.ToDictionary()
             };
 
             if (args is SlashCommandProperties slashProps)
@@ -299,6 +309,8 @@ namespace Discord.Rest
                 DefaultPermission = arg.IsDefaultPermission.IsSpecified
                         ? arg.IsDefaultPermission.Value
                         : Optional<bool>.Unspecified,
+                NameLocalizations = arg.NameLocalizations?.ToDictionary(),
+                DescriptionLocalizations = arg.DescriptionLocalizations?.ToDictionary(),
 
                 // TODO: better conversion to nullable optionals
                 DefaultMemberPermission = arg.DefaultMemberPermissions.ToNullable(),
@@ -335,7 +347,9 @@ namespace Discord.Rest
                 Name = arg.Name,
                 DefaultPermission = arg.IsDefaultPermission.IsSpecified
                         ? arg.IsDefaultPermission.Value
-                        : Optional<bool>.Unspecified
+                        : Optional<bool>.Unspecified,
+                NameLocalizations = arg.NameLocalizations?.ToDictionary(),
+                DescriptionLocalizations = arg.DescriptionLocalizations?.ToDictionary()
             };
 
             if (arg is SlashCommandProperties slashProps)

src/Discord.Net.Rest/Entities/Interactions/RestApplicationCommand.cs

@@ -38,6 +38,32 @@ namespace Discord.Rest
         /// </summary>
         public IReadOnlyCollection<RestApplicationCommandOption> Options { get; private set; }
 
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> NameLocalizations { get; private set; }
+
+        /// <summary>
+        ///     Gets the localization dictionary for the description field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> DescriptionLocalizations { get; private set; }
+
+        /// <summary>
+        ///     Gets the localized name of this command.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        public string NameLocalized { get; private set; }
+
+        /// <summary>
+        ///     Gets the localized description of this command.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        public string DescriptionLocalized { get; private set; }
+
         /// <inheritdoc/>
         public DateTimeOffset CreatedAt
             => SnowflakeUtils.FromSnowflake(Id);
@@ -64,6 +90,15 @@ namespace Discord.Rest
                 ? model.Options.Value.Select(RestApplicationCommandOption.Create).ToImmutableArray()
                 : ImmutableArray.Create<RestApplicationCommandOption>();
 
+            NameLocalizations = model.NameLocalizations.GetValueOrDefault(null)?.ToImmutableDictionary() ??
+                                ImmutableDictionary<string, string>.Empty;
+
+            DescriptionLocalizations = model.DescriptionLocalizations.GetValueOrDefault(null)?.ToImmutableDictionary() ??
+                                ImmutableDictionary<string, string>.Empty;
+
+            NameLocalized = model.NameLocalized.GetValueOrDefault();
+            DescriptionLocalized = model.DescriptionLocalized.GetValueOrDefault();
+            
             IsEnabledInDm = model.DmPermission.GetValueOrDefault(true).GetValueOrDefault(true);
             DefaultMemberPermissions = new GuildPermissions((ulong)model.DefaultMemberPermission.GetValueOrDefault(0).GetValueOrDefault(0));
         }

src/Discord.Net.Rest/Entities/Interactions/RestApplicationCommandChoice.cs

@@ -1,3 +1,5 @@
+using System.Collections.Generic;
+using System.Collections.Immutable;
 using Model = Discord.API.ApplicationCommandOptionChoice;
 
 namespace Discord.Rest
@@ -13,10 +15,25 @@ namespace Discord.Rest
         /// <inheritdoc/>
         public object Value { get; }
 
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command option choice.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> NameLocalizations { get; }
+
+        /// <summary>
+        ///     Gets the localized name of this command option choice.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        public string NameLocalized { get; }
+
         internal RestApplicationCommandChoice(Model model)
         {
             Name = model.Name;
             Value = model.Value;
+            NameLocalizations = model.NameLocalizations.GetValueOrDefault(null)?.ToImmutableDictionary();
+            NameLocalized = model.NameLocalized.GetValueOrDefault(null);
         }
     }
 }

src/Discord.Net.Rest/Entities/Interactions/RestApplicationCommandOption.cs

@@ -27,7 +27,7 @@ namespace Discord.Rest
         public bool? IsRequired { get; private set; }
 
         /// <inheritdoc/>
-        public bool? IsAutocomplete { get; private set; } 
+        public bool? IsAutocomplete { get; private set; }
 
         /// <inheritdoc/>
         public double? MinValue { get; private set; }
@@ -54,6 +54,32 @@ namespace Discord.Rest
         /// <inheritdoc/>
         public IReadOnlyCollection<ChannelType> ChannelTypes { get; private set; }
 
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command option.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> NameLocalizations { get; private set; }
+
+        /// <summary>
+        ///     Gets the localization dictionary for the description field of this command option.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> DescriptionLocalizations { get; private set; }
+
+        /// <summary>
+        ///     Gets the localized name of this command option.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        public string NameLocalized { get; private set; }
+
+        /// <summary>
+        ///     Gets the localized description of this command option.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        public string DescriptionLocalized { get; private set; }
+
         internal RestApplicationCommandOption() { }
 
         internal static RestApplicationCommandOption Create(Model model)
@@ -98,6 +124,15 @@ namespace Discord.Rest
             ChannelTypes = model.ChannelTypes.IsSpecified
                 ? model.ChannelTypes.Value.ToImmutableArray()
                 : ImmutableArray.Create<ChannelType>();
+
+            NameLocalizations = model.NameLocalizations.GetValueOrDefault(null)?.ToImmutableDictionary() ??
+                                ImmutableDictionary<string, string>.Empty;
+
+            DescriptionLocalizations = model.DescriptionLocalizations.GetValueOrDefault(null)?.ToImmutableDictionary() ??
+                                       ImmutableDictionary<string, string>.Empty;
+
+            NameLocalized = model.NameLocalized.GetValueOrDefault();
+            DescriptionLocalized = model.DescriptionLocalized.GetValueOrDefault();
         }
         #endregion
 

src/Discord.Net.Rest/Net/DefaultRestClient.cs

@@ -66,33 +66,45 @@ namespace Discord.Net.Rest
             _cancelToken = cancelToken;
         }
 
-        public async Task<RestResponse> SendAsync(string method, string endpoint, CancellationToken cancelToken, bool headerOnly, string reason = null)
+        public async Task<RestResponse> SendAsync(string method, string endpoint, CancellationToken cancelToken, bool headerOnly, string reason = null,
+            IEnumerable<KeyValuePair<string, IEnumerable<string>>> requestHeaders = null)
         {
             string uri = Path.Combine(_baseUrl, endpoint);
             using (var restRequest = new HttpRequestMessage(GetMethod(method), uri))
             {
                 if (reason != null) restRequest.Headers.Add("X-Audit-Log-Reason", Uri.EscapeDataString(reason));
+                if (requestHeaders != null)
+                    foreach (var header in requestHeaders)
+                        restRequest.Headers.Add(header.Key, header.Value);
                 return await SendInternalAsync(restRequest, cancelToken, headerOnly).ConfigureAwait(false);
             }
         }
-        public async Task<RestResponse> SendAsync(string method, string endpoint, string json, CancellationToken cancelToken, bool headerOnly, string reason = null)
+        public async Task<RestResponse> SendAsync(string method, string endpoint, string json, CancellationToken cancelToken, bool headerOnly, string reason = null,
+            IEnumerable<KeyValuePair<string, IEnumerable<string>>> requestHeaders = null)
         {
             string uri = Path.Combine(_baseUrl, endpoint);
             using (var restRequest = new HttpRequestMessage(GetMethod(method), uri))
             {
                 if (reason != null) restRequest.Headers.Add("X-Audit-Log-Reason", Uri.EscapeDataString(reason));
+                if (requestHeaders != null)
+                    foreach (var header in requestHeaders)
+                        restRequest.Headers.Add(header.Key, header.Value);
                 restRequest.Content = new StringContent(json, Encoding.UTF8, "application/json");
                 return await SendInternalAsync(restRequest, cancelToken, headerOnly).ConfigureAwait(false);
             }
         }
 
         /// <exception cref="InvalidOperationException">Unsupported param type.</exception>
-        public async Task<RestResponse> SendAsync(string method, string endpoint, IReadOnlyDictionary<string, object> multipartParams, CancellationToken cancelToken, bool headerOnly, string reason = null)
+        public async Task<RestResponse> SendAsync(string method, string endpoint, IReadOnlyDictionary<string, object> multipartParams, CancellationToken cancelToken, bool headerOnly, string reason = null,
+            IEnumerable<KeyValuePair<string, IEnumerable<string>>> requestHeaders = null)
         {
             string uri = Path.Combine(_baseUrl, endpoint);
             using (var restRequest = new HttpRequestMessage(GetMethod(method), uri))
             {
                 if (reason != null) restRequest.Headers.Add("X-Audit-Log-Reason", Uri.EscapeDataString(reason));
+                if (requestHeaders != null)
+                    foreach (var header in requestHeaders)
+                        restRequest.Headers.Add(header.Key, header.Value);
                 var content = new MultipartFormDataContent("Upload----" + DateTime.Now.ToString(CultureInfo.InvariantCulture));
                 MemoryStream memoryStream = null;
                 if (multipartParams != null)
@@ -126,7 +138,7 @@ namespace Discord.Net.Rest
 
                                 content.Add(streamContent, p.Key, fileValue.Filename);
 #pragma warning restore IDISP004
-                                    
+
                                 continue;
                             }
                             default:

src/Discord.Net.Rest/Net/Queue/Requests/RestRequest.cs

@@ -1,5 +1,8 @@
 using Discord.Net.Rest;
 using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.IO;
 using System.Threading.Tasks;
 
@@ -28,7 +31,7 @@ namespace Discord.Net.Queue
 
         public virtual async Task<RestResponse> SendAsync()
         {
-            return await Client.SendAsync(Method, Endpoint, Options.CancelToken, Options.HeaderOnly, Options.AuditLogReason).ConfigureAwait(false);
+            return await Client.SendAsync(Method, Endpoint, Options.CancelToken, Options.HeaderOnly, Options.AuditLogReason, Options.RequestHeaders).ConfigureAwait(false);
         }
     }
 }

src/Discord.Net.WebSocket/DiscordSocketClient.cs

@@ -450,14 +450,16 @@ namespace Discord.WebSocket
         /// <summary>
         ///     Gets a collection of all global commands.
         /// </summary>
+        /// <param name="withLocalizations">Whether to include full localization dictionaries in the returned objects, instead of the name localized and description localized fields.</param>
+        /// <param name="locale">The target locale of the localized name and description fields. Sets <c>X-Discord-Locale</c> header, which takes precedence over <c>Accept-Language</c>.</param>
         /// <param name="options">The options to be used when sending the request.</param>
         /// <returns>
         ///     A task that represents the asynchronous get operation. The task result contains a read-only collection of global
         ///     application commands.
         /// </returns>
-        public async Task<IReadOnlyCollection<SocketApplicationCommand>> GetGlobalApplicationCommandsAsync(RequestOptions options = null)
+        public async Task<IReadOnlyCollection<SocketApplicationCommand>> GetGlobalApplicationCommandsAsync(bool withLocalizations = false, string locale = null, RequestOptions options = null)
         {
-            var commands = (await ApiClient.GetGlobalApplicationCommandsAsync(options)).Select(x => SocketApplicationCommand.Create(this, x));
+            var commands = (await ApiClient.GetGlobalApplicationCommandsAsync(withLocalizations, locale, options)).Select(x => SocketApplicationCommand.Create(this, x));
 
             foreach(var command in commands)
             {
@@ -3236,8 +3238,8 @@ namespace Discord.WebSocket
         async Task<IApplicationCommand> IDiscordClient.GetGlobalApplicationCommandAsync(ulong id, RequestOptions options)
             => await GetGlobalApplicationCommandAsync(id, options);
         /// <inheritdoc />
-        async Task<IReadOnlyCollection<IApplicationCommand>> IDiscordClient.GetGlobalApplicationCommandsAsync(RequestOptions options)
-            => await GetGlobalApplicationCommandsAsync(options);
+        async Task<IReadOnlyCollection<IApplicationCommand>> IDiscordClient.GetGlobalApplicationCommandsAsync(bool withLocalizations, string locale, RequestOptions options)
+            => await GetGlobalApplicationCommandsAsync(withLocalizations, locale, options);
 
         /// <inheritdoc />
         async Task IDiscordClient.StartAsync()

src/Discord.Net.WebSocket/Entities/Guilds/SocketGuild.cs

@@ -874,14 +874,17 @@ namespace Discord.WebSocket
         /// <summary>
         ///     Gets a collection of slash commands created by the current user in this guild.
         /// </summary>
+        /// <param name="withLocalizations">Whether to include full localization dictionaries in the returned objects, instead of the name localized and description localized fields.</param>
+        /// <param name="locale">The target locale of the localized name and description fields. Sets <c>X-Discord-Locale</c> header, which takes precedence over <c>Accept-Language</c>.</param>
         /// <param name="options">The options to be used when sending the request.</param>
         /// <returns>
         ///     A task that represents the asynchronous get operation. The task result contains a read-only collection of
         ///     slash commands created by the current user.
         /// </returns>
-        public async Task<IReadOnlyCollection<SocketApplicationCommand>> GetApplicationCommandsAsync(RequestOptions options = null)
+        public async Task<IReadOnlyCollection<SocketApplicationCommand>> GetApplicationCommandsAsync(bool withLocalizations = false, string locale = null, RequestOptions options = null)
         {
-            var commands = (await Discord.ApiClient.GetGuildApplicationCommandsAsync(Id, options)).Select(x => SocketApplicationCommand.Create(Discord, x, Id));
+            var commands = (await Discord.ApiClient.GetGuildApplicationCommandsAsync(Id, withLocalizations, locale, options))
+                .Select(x => SocketApplicationCommand.Create(Discord, x, Id));
 
             foreach (var command in commands)
             {
@@ -1977,8 +1980,8 @@ namespace Discord.WebSocket
         async Task<IReadOnlyCollection<IWebhook>> IGuild.GetWebhooksAsync(RequestOptions options)
             => await GetWebhooksAsync(options).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IReadOnlyCollection<IApplicationCommand>> IGuild.GetApplicationCommandsAsync (RequestOptions options)
-            => await GetApplicationCommandsAsync(options).ConfigureAwait(false);
+        async Task<IReadOnlyCollection<IApplicationCommand>> IGuild.GetApplicationCommandsAsync (bool withLocalizations, string locale, RequestOptions options)
+            => await GetApplicationCommandsAsync(withLocalizations, locale, options).ConfigureAwait(false);
         /// <inheritdoc />
         async Task<ICustomSticker> IGuild.CreateStickerAsync(string name, string description, IEnumerable<string> tags, Image image, RequestOptions options)
             => await CreateStickerAsync(name, description, tags, image, options);

src/Discord.Net.WebSocket/Entities/Interaction/SocketBaseCommand/SocketApplicationCommand.cs

@@ -50,6 +50,32 @@ namespace Discord.WebSocket
         /// </remarks>
         public IReadOnlyCollection<SocketApplicationCommandOption> Options { get; private set; }
 
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> NameLocalizations { get; private set; }
+
+        /// <summary>
+        ///     Gets the localization dictionary for the description field of this command.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> DescriptionLocalizations { get; private set; }
+
+        /// <summary>
+        ///     Gets the localized name of this command.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        public string NameLocalized { get; private set; }
+
+        /// <summary>
+        ///     Gets the localized description of this command.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        public string DescriptionLocalized { get; private set; }
+
         /// <inheritdoc/>
         public DateTimeOffset CreatedAt
             => SnowflakeUtils.FromSnowflake(Id);
@@ -93,6 +119,15 @@ namespace Discord.WebSocket
                 ? model.Options.Value.Select(SocketApplicationCommandOption.Create).ToImmutableArray()
                 : ImmutableArray.Create<SocketApplicationCommandOption>();
 
+            NameLocalizations = model.NameLocalizations.GetValueOrDefault(null)?.ToImmutableDictionary() ??
+                                ImmutableDictionary<string, string>.Empty;
+
+            DescriptionLocalizations = model.DescriptionLocalizations.GetValueOrDefault(null)?.ToImmutableDictionary() ??
+                                       ImmutableDictionary<string, string>.Empty;
+
+            NameLocalized = model.NameLocalized.GetValueOrDefault();
+            DescriptionLocalized = model.DescriptionLocalized.GetValueOrDefault();
+
             IsEnabledInDm = model.DmPermission.GetValueOrDefault(true).GetValueOrDefault(true);
             DefaultMemberPermissions = new GuildPermissions((ulong)model.DefaultMemberPermission.GetValueOrDefault(0).GetValueOrDefault(0));
         }

src/Discord.Net.WebSocket/Entities/Interaction/SocketBaseCommand/SocketApplicationCommandChoice.cs

@@ -1,3 +1,5 @@
+using System.Collections.Generic;
+using System.Collections.Immutable;
 using Model = Discord.API.ApplicationCommandOptionChoice;
 
 namespace Discord.WebSocket
@@ -13,6 +15,19 @@ namespace Discord.WebSocket
         /// <inheritdoc/>
         public object Value { get; private set; }
 
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command option choice.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> NameLocalizations { get; private set; }
+
+        /// <summary>
+        ///     Gets the localized name of this command option choice.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        public string NameLocalized { get; private set; }
+
         internal SocketApplicationCommandChoice() { }
         internal static SocketApplicationCommandChoice Create(Model model)
         {
@@ -24,6 +39,8 @@ namespace Discord.WebSocket
         {
             Name = model.Name;
             Value = model.Value;
+            NameLocalizations = model.NameLocalizations.GetValueOrDefault(null)?.ToImmutableDictionary();
+            NameLocalized = model.NameLocalized.GetValueOrDefault(null);
         }
     }
 }

src/Discord.Net.WebSocket/Entities/Interaction/SocketBaseCommand/SocketApplicationCommandOption.cs

@@ -54,6 +54,32 @@ namespace Discord.WebSocket
         /// </summary>
         public IReadOnlyCollection<ChannelType> ChannelTypes { get; private set; }
 
+        /// <summary>
+        ///     Gets the localization dictionary for the name field of this command option.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> NameLocalizations { get; private set; }
+
+        /// <summary>
+        ///     Gets the localization dictionary for the description field of this command option.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> DescriptionLocalizations { get; private set; }
+
+        /// <summary>
+        ///     Gets the localized name of this command option.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        public string NameLocalized { get; private set; }
+
+        /// <summary>
+        ///     Gets the localized description of this command option.
+        /// </summary>
+        /// <remarks>
+        ///     Only returned when the `withLocalizations` query parameter is set to <see langword="false"/> when requesting the command.
+        /// </remarks>
+        public string DescriptionLocalized { get; private set; }
+
         internal SocketApplicationCommandOption() { }
         internal static SocketApplicationCommandOption Create(Model model)
         {
@@ -92,6 +118,15 @@ namespace Discord.WebSocket
             ChannelTypes = model.ChannelTypes.IsSpecified
                 ? model.ChannelTypes.Value.ToImmutableArray()
                 : ImmutableArray.Create<ChannelType>();
+
+            NameLocalizations = model.NameLocalizations.GetValueOrDefault(null)?.ToImmutableDictionary() ??
+                                ImmutableDictionary<string, string>.Empty;
+
+            DescriptionLocalizations = model.DescriptionLocalizations.GetValueOrDefault(null)?.ToImmutableDictionary() ??
+                                       ImmutableDictionary<string, string>.Empty;
+
+            NameLocalized = model.NameLocalized.GetValueOrDefault();
+            DescriptionLocalized = model.DescriptionLocalized.GetValueOrDefault();
         }
 
         IReadOnlyCollection<IApplicationCommandOptionChoice> IApplicationCommandOption.Choices => Choices;