diff --git a/CHANGELOG.md b/CHANGELOG.md
index f9f7484dda..b9f80096ad 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,8 @@
         * `Klock`: `2.2.0` -> `2.3.1`
         * `Ktor`: `1.6.1` -> `1.6.2`
         * `MicroUtils`: `0.5.16` -> `0.5.18`
+* `Core`:
+    * Support of strongly-typed ietf language codes has been added
 * `API`:
     * New extension `TelegramBot#downloadFile` for any `MediaContent`
 * `Behaviour Builder`:
diff --git a/tgbotapi.core/build.gradle b/tgbotapi.core/build.gradle
index 1948d03bc0..83582016f5 100644
--- a/tgbotapi.core/build.gradle
+++ b/tgbotapi.core/build.gradle
@@ -51,6 +51,7 @@ kotlin {
                 api "dev.inmo:micro_utils.serialization.base64:$micro_utils_version"
                 api "dev.inmo:micro_utils.serialization.encapsulator:$micro_utils_version"
                 api "dev.inmo:micro_utils.serialization.typed_serializer:$micro_utils_version"
+                api "dev.inmo:micro_utils.language_codes:$micro_utils_version"
 
                 api "io.ktor:ktor-client-core:$ktor_version"
             }
diff --git a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/CommonAbstracts/WithLanguageCode.kt b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/CommonAbstracts/WithLanguageCode.kt
new file mode 100644
index 0000000000..d59d9c9cce
--- /dev/null
+++ b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/CommonAbstracts/WithLanguageCode.kt
@@ -0,0 +1,17 @@
+package dev.inmo.tgbotapi.CommonAbstracts
+
+import dev.inmo.micro_utils.language_codes.IetfLanguageCode
+
+interface WithOptionalLanguageCode {
+    val ietfLanguageCode: IetfLanguageCode?
+
+    val languageCode: String?
+        get() = ietfLanguageCode ?.code
+}
+
+interface WithLanguageCode : WithOptionalLanguageCode {
+    override val ietfLanguageCode: IetfLanguageCode
+
+    override val languageCode: String
+        get() = ietfLanguageCode.code
+}
diff --git a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/BotCommand.kt b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/BotCommand.kt
index bc6b7cac0b..e5fb89c6c3 100644
--- a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/BotCommand.kt
+++ b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/BotCommand.kt
@@ -1,9 +1,9 @@
 package dev.inmo.tgbotapi.requests.bot
 
+import dev.inmo.tgbotapi.CommonAbstracts.WithOptionalLanguageCode
 import dev.inmo.tgbotapi.requests.abstracts.SimpleRequest
 import dev.inmo.tgbotapi.types.commands.BotCommandScope
 
-sealed interface MyCommandsRequest<T : Any> : SimpleRequest<T> {
+sealed interface MyCommandsRequest<T : Any> : SimpleRequest<T>, WithOptionalLanguageCode {
     val scope: BotCommandScope
-    val languageCode: String?
 }
diff --git a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/DeleteMyCommands.kt b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/DeleteMyCommands.kt
index 867b5fc978..61b01180cb 100644
--- a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/DeleteMyCommands.kt
+++ b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/DeleteMyCommands.kt
@@ -1,8 +1,9 @@
 package dev.inmo.tgbotapi.requests.bot
 
+import dev.inmo.micro_utils.language_codes.IetfLanguageCode
+import dev.inmo.micro_utils.language_codes.IetfLanguageCodeSerializer
+import dev.inmo.tgbotapi.types.*
 import dev.inmo.tgbotapi.types.commands.*
-import dev.inmo.tgbotapi.types.languageCodeField
-import dev.inmo.tgbotapi.types.scopeField
 import kotlinx.serialization.*
 import kotlinx.serialization.builtins.serializer
 
@@ -12,11 +13,20 @@ data class DeleteMyCommands(
     @Serializable(BotCommandScopeSerializer::class)
     override val scope: BotCommandScope = BotCommandScopeDefault,
     @SerialName(languageCodeField)
-    override val languageCode: String? = null
+    @Serializable(IetfLanguageCodeSerializer::class)
+    override val ietfLanguageCode: IetfLanguageCode? = null
 ) : MyCommandsRequest<Boolean> {
     override fun method(): String  = "deleteMyCommands"
     override val requestSerializer: SerializationStrategy<DeleteMyCommands> = serializer()
     override val resultDeserializer: DeserializationStrategy<Boolean> = Boolean.serializer()
 
+    constructor(
+        scope: BotCommandScope = BotCommandScopeDefault,
+        languageCode: String?
+    ) : this(
+        scope,
+        languageCode ?.let(::IetfLanguageCode)
+    )
+
     companion object : MyCommandsRequest<Boolean> by DeleteMyCommands()
 }
diff --git a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/GetMyCommands.kt b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/GetMyCommands.kt
index 31b8fe194a..511fc9e33f 100644
--- a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/GetMyCommands.kt
+++ b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/GetMyCommands.kt
@@ -1,5 +1,7 @@
 package dev.inmo.tgbotapi.requests.bot
 
+import dev.inmo.micro_utils.language_codes.IetfLanguageCode
+import dev.inmo.micro_utils.language_codes.IetfLanguageCodeSerializer
 import dev.inmo.tgbotapi.types.*
 import dev.inmo.tgbotapi.types.commands.*
 import kotlinx.serialization.*
@@ -13,7 +15,8 @@ data class GetMyCommands(
     @Serializable(BotCommandScopeSerializer::class)
     override val scope: BotCommandScope = BotCommandScopeDefault,
     @SerialName(languageCodeField)
-    override val languageCode: String? = null
+    @Serializable(IetfLanguageCodeSerializer::class)
+    override val ietfLanguageCode: IetfLanguageCode? = null
 ) : MyCommandsRequest<List<BotCommand>> {
     override fun method(): String = "getMyCommands"
     override val resultDeserializer: DeserializationStrategy<List<BotCommand>>
@@ -21,5 +24,13 @@ data class GetMyCommands(
     override val requestSerializer: SerializationStrategy<*>
         get() = serializer()
 
+    constructor(
+        scope: BotCommandScope = BotCommandScopeDefault,
+        languageCode: String?
+    ) : this(
+        scope,
+        languageCode ?.let(::IetfLanguageCode)
+    )
+
     companion object : MyCommandsRequest<List<BotCommand>> by GetMyCommands()
 }
diff --git a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/SetMyCommands.kt b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/SetMyCommands.kt
index 4f926840e2..6df10c13b1 100644
--- a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/SetMyCommands.kt
+++ b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/bot/SetMyCommands.kt
@@ -1,5 +1,7 @@
 package dev.inmo.tgbotapi.requests.bot
 
+import dev.inmo.micro_utils.language_codes.IetfLanguageCode
+import dev.inmo.micro_utils.language_codes.IetfLanguageCodeSerializer
 import dev.inmo.tgbotapi.types.*
 import dev.inmo.tgbotapi.types.commands.*
 import kotlinx.serialization.*
@@ -13,7 +15,8 @@ class SetMyCommands(
     @Serializable(BotCommandScopeSerializer::class)
     override val scope: BotCommandScope = BotCommandScopeDefault,
     @SerialName(languageCodeField)
-    override val languageCode: String? = null
+    @Serializable(IetfLanguageCodeSerializer::class)
+    override val ietfLanguageCode: IetfLanguageCode? = null
 ) : MyCommandsRequest<Boolean> {
     override fun method(): String = "setMyCommands"
     override val resultDeserializer: DeserializationStrategy<Boolean>
@@ -21,6 +24,16 @@ class SetMyCommands(
     override val requestSerializer: SerializationStrategy<*>
         get() = serializer()
 
+    constructor(
+        commands: List<BotCommand>,
+        scope: BotCommandScope = BotCommandScopeDefault,
+        languageCode: String?
+    ) : this(
+        commands,
+        scope,
+        languageCode ?.let(::IetfLanguageCode)
+    )
+
     init {
         if (commands.size !in botCommandsLimit) {
             error("Bot commands list size able to be in range $botCommandsLimit, but incoming size is ${commands.size}")
diff --git a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/types/User.kt b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/types/User.kt
index bcc2ea2875..b8774ea67c 100644
--- a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/types/User.kt
+++ b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/types/User.kt
@@ -1,5 +1,8 @@
 package dev.inmo.tgbotapi.types
 
+import dev.inmo.micro_utils.language_codes.IetfLanguageCode
+import dev.inmo.micro_utils.language_codes.IetfLanguageCodeSerializer
+import dev.inmo.tgbotapi.CommonAbstracts.WithOptionalLanguageCode
 import dev.inmo.tgbotapi.types.chat.abstracts.PrivateChat
 import dev.inmo.tgbotapi.types.chat.extended.ExtendedPrivateChatImpl
 import dev.inmo.tgbotapi.utils.*
@@ -22,8 +25,17 @@ data class CommonUser(
     @SerialName(usernameField)
     override val username: Username? = null,
     @SerialName(languageCodeField)
-    val languageCode: String? = null
-) : User()
+    @Serializable(IetfLanguageCodeSerializer::class)
+    override val ietfLanguageCode: IetfLanguageCode? = null
+) : User(), WithOptionalLanguageCode {
+    constructor(
+        id: UserId,
+        firstName: String,
+        lastName: String = "",
+        username: Username? = null,
+        languageCode: String
+    ) : this(id, firstName, lastName, username, IetfLanguageCode(languageCode))
+}
 
 @PreviewFeature
 typealias ExtendedUser = ExtendedPrivateChatImpl
diff --git a/tgbotapi.core/src/jvmMain/kotlin/dev/inmo/tgbotapi/types/UserLocale.kt b/tgbotapi.core/src/jvmMain/kotlin/dev/inmo/tgbotapi/types/UserLocale.kt
index 33e7b5920b..d2e9da4d08 100644
--- a/tgbotapi.core/src/jvmMain/kotlin/dev/inmo/tgbotapi/types/UserLocale.kt
+++ b/tgbotapi.core/src/jvmMain/kotlin/dev/inmo/tgbotapi/types/UserLocale.kt
@@ -1,7 +1,8 @@
 package dev.inmo.tgbotapi.types
 
+import dev.inmo.micro_utils.language_codes.IetfLanguageCode
+import dev.inmo.tgbotapi.CommonAbstracts.WithLanguageCode
 import java.util.*
 
-fun CommonUser.javaLocale(): Locale? = languageCode ?.let {
-    Locale.forLanguageTag(it)
-}
+fun IetfLanguageCode?.javaLocale() = this ?.code ?.let { Locale.forLanguageTag(it) }
+fun WithLanguageCode?.javaLocale() = this ?.ietfLanguageCode.javaLocale()
diff --git a/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/DeleteMyCommands.kt b/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/DeleteMyCommands.kt
index 31abad88f5..3995e5384a 100644
--- a/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/DeleteMyCommands.kt
+++ b/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/DeleteMyCommands.kt
@@ -1,5 +1,6 @@
 package dev.inmo.tgbotapi.extensions.api.bot
 
+import dev.inmo.micro_utils.language_codes.IetfLanguageCode
 import dev.inmo.tgbotapi.bot.TelegramBot
 import dev.inmo.tgbotapi.requests.bot.DeleteMyCommands
 import dev.inmo.tgbotapi.types.commands.BotCommandScope
@@ -7,5 +8,10 @@ import dev.inmo.tgbotapi.types.commands.BotCommandScopeDefault
 
 suspend fun TelegramBot.deleteMyCommands(
     scope: BotCommandScope = BotCommandScopeDefault,
-    languageCode: String? = null
+    languageCode: IetfLanguageCode?
 ) = execute(DeleteMyCommands(scope, languageCode))
+
+suspend fun TelegramBot.deleteMyCommands(
+    scope: BotCommandScope = BotCommandScopeDefault,
+    languageCode: String? = null
+) = deleteMyCommands(scope, languageCode ?.let(::IetfLanguageCode))
diff --git a/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/GetMyCommands.kt b/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/GetMyCommands.kt
index 07a0c6a3ac..59fb66828d 100644
--- a/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/GetMyCommands.kt
+++ b/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/GetMyCommands.kt
@@ -1,5 +1,6 @@
 package dev.inmo.tgbotapi.extensions.api.bot
 
+import dev.inmo.micro_utils.language_codes.IetfLanguageCode
 import dev.inmo.tgbotapi.bot.TelegramBot
 import dev.inmo.tgbotapi.requests.bot.GetMyCommands
 import dev.inmo.tgbotapi.types.commands.BotCommandScope
@@ -7,5 +8,10 @@ import dev.inmo.tgbotapi.types.commands.BotCommandScopeDefault
 
 suspend fun TelegramBot.getMyCommands(
     scope: BotCommandScope = BotCommandScopeDefault,
-    languageCode: String? = null
+    languageCode: IetfLanguageCode? = null
 ) = execute(GetMyCommands(scope, languageCode))
+
+suspend fun TelegramBot.getMyCommands(
+    scope: BotCommandScope = BotCommandScopeDefault,
+    languageCode: String? = null
+) = getMyCommands(scope, languageCode ?.let(::IetfLanguageCode))
diff --git a/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/SetMyCommands.kt b/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/SetMyCommands.kt
index d0d8b0a8cc..e7f5ef01bc 100644
--- a/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/SetMyCommands.kt
+++ b/tgbotapi.extensions.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/bot/SetMyCommands.kt
@@ -1,5 +1,6 @@
 package dev.inmo.tgbotapi.extensions.api.bot
 
+import dev.inmo.micro_utils.language_codes.IetfLanguageCode
 import dev.inmo.tgbotapi.bot.TelegramBot
 import dev.inmo.tgbotapi.requests.bot.SetMyCommands
 import dev.inmo.tgbotapi.types.BotCommand
@@ -9,9 +10,21 @@ import dev.inmo.tgbotapi.types.commands.BotCommandScopeDefault
 suspend fun TelegramBot.setMyCommands(
     commands: List<BotCommand>,
     scope: BotCommandScope = BotCommandScopeDefault,
-    languageCode: String? = null
+    languageCode: IetfLanguageCode?
 ) = execute(SetMyCommands(commands, scope, languageCode))
 
+suspend fun TelegramBot.setMyCommands(
+    vararg commands: BotCommand,
+    scope: BotCommandScope = BotCommandScopeDefault,
+    languageCode: IetfLanguageCode?
+) = setMyCommands(commands.toList(), scope, languageCode)
+
+suspend fun TelegramBot.setMyCommands(
+    commands: List<BotCommand>,
+    scope: BotCommandScope = BotCommandScopeDefault,
+    languageCode: String? = null
+) = setMyCommands(commands, scope, languageCode ?.let(::IetfLanguageCode))
+
 suspend fun TelegramBot.setMyCommands(
     vararg commands: BotCommand,
     scope: BotCommandScope = BotCommandScopeDefault,