diff --git a/packages/backend/migration/1706827327619-add-language-selector.js b/packages/backend/migration/1706827327619-add-language-selector.js
new file mode 100644
index 000000000..840ec7711
--- /dev/null
+++ b/packages/backend/migration/1706827327619-add-language-selector.js
@@ -0,0 +1,11 @@
+export class AddLanguageSelector1706827327619 {
+	async up(queryRunner) {
+		await queryRunner.query(
+			`ALTER TABLE "note" ADD "lang" character varying(10)`,
+		);
+	}
+
+	async down(queryRunner) {
+		await queryRunner.query(`ALTER TABLE "note" DROP COLUMN "lang"`);
+	}
+}
diff --git a/packages/backend/src/core/NoteCreateService.ts b/packages/backend/src/core/NoteCreateService.ts
index 8a43e100d..708f80d14 100644
--- a/packages/backend/src/core/NoteCreateService.ts
+++ b/packages/backend/src/core/NoteCreateService.ts
@@ -72,6 +72,7 @@ import { trackPromise } from '@/misc/promise-tracker.js';
 import { isNotNull } from '@/misc/is-not-null.js';
 import { IdentifiableError } from '@/misc/identifiable-error.js';
 import { CollapsedQueue } from '@/misc/collapsed-queue.js';
+import { SUPPORTED_POST_LOCALES } from "@/misc/langmap.js";
 
 type NotificationType = 'reply' | 'renote' | 'quote' | 'mention';
 
@@ -342,6 +343,15 @@ export class NoteCreateService implements OnApplicationShutdown {
 			data.text = null;
 		}
 
+		if (data.lang) {
+			if (!Object.keys(SUPPORTED_POST_LOCALES).includes(data.lang.toLowerCase())) {
+				throw new Error("invalid lang param");
+			}
+			data.lang = data.lang.toLowerCase();
+		} else {
+			data.lang = null;
+		}
+
 		let tags = data.apHashtags;
 		let emojis = data.apEmojis;
 		let mentionedUsers = data.apMentions;
@@ -458,6 +468,7 @@ export class NoteCreateService implements OnApplicationShutdown {
 				: null,
 			name: data.name,
 			text: data.text,
+			lang: data.lang,
 			hasPoll: data.poll != null,
 			cw: data.cw ?? null,
 			tags: tags.map(tag => normalizeForSearch(tag)),
diff --git a/packages/backend/src/core/activitypub/models/ApNoteService.ts b/packages/backend/src/core/activitypub/models/ApNoteService.ts
index 9effcfac9..7eee22e4e 100644
--- a/packages/backend/src/core/activitypub/models/ApNoteService.ts
+++ b/packages/backend/src/core/activitypub/models/ApNoteService.ts
@@ -39,6 +39,7 @@ import { ApQuestionService } from './ApQuestionService.js';
 import { ApImageService } from './ApImageService.js';
 import type { Resolver } from '../ApResolverService.js';
 import type { IObject, IPost } from '../type.js';
+import {Obj} from "@/misc/json-schema.js";
 
 @Injectable()
 export class ApNoteService {
@@ -204,12 +205,17 @@ export class ApNoteService {
 
 		// テキストのパース
 		let text: string | null = null;
-		if (note.source?.mediaType === 'text/x.misskeymarkdown' && typeof note.source.content === 'string') {
-			text = note.source.content;
+		let lang: string | null = null;
+		if (note.source?.mediaType === 'text/x.misskeymarkdown' && (typeof note.source.content === 'string' || note.source.contentMap)) {
+			const guessed = this.guessLang(note.source);
+			text = guessed.text;
+			lang = guessed.lang;
 		} else if (typeof note._misskey_content !== 'undefined') {
 			text = note._misskey_content;
-		} else if (typeof note.content === 'string') {
-			text = this.apMfmService.htmlToMfm(note.content, note.tag);
+		} else if (typeof note.content === 'string' || note.contentMap) {
+			const guessed = this.guessLang(note);
+			lang = guessed.lang;
+			if (guessed.text) text = this.apMfmService.htmlToMfm(guessed.text, note.tag);
 		}
 
 		const poll = await this.apQuestionService.extractPollFromQuestion(note, resolver).catch(() => undefined);
@@ -343,6 +349,7 @@ export class ApNoteService {
 				name: note.name,
 				cw,
 				text,
+				lang,
 				localOnly: false,
 				visibility,
 				visibleUsers,
@@ -460,4 +467,40 @@ export class ApNoteService {
 			}).then(x => this.emojisRepository.findOneByOrFail(x.identifiers[0]));
 		}));
 	}
+
+	@bindThis
+	private guessLang(source: { contentMap?: Record<string, string | null>, content?: string | null }): { lang: string | null, text: string | null } {
+		// do we have a map?
+		if (source.contentMap) {
+			const entries = Object.entries(source.contentMap);
+
+			// only one entry: take that
+			if (entries.length === 1) {
+				return { lang: entries[0][0], text: entries[0][1] };
+			}
+
+			// did the sender indicate a preferred language?
+			if (source.content) {
+				for (const e of entries) {
+					if (e[1] === source.content) {
+						return { lang: e[0], text: e[1] };
+					}
+				}
+			}
+
+			// can we find one of *our* preferred languages?
+			// for (const prefLang of this.config.langPref) {
+			// 	if (source.contentMap[prefLang]) {
+			// 		return { lang: prefLang, text: source.contentMap[prefLang] };
+			// 	}
+			// }
+
+			// bah, just pick one
+			return { lang: entries[0][0], text: entries[0][1] };
+		}
+
+		// no map, so we don't know the language, just take whatever
+		// content we got
+		return { lang: null, text: source.content ?? null };
+	}
 }
diff --git a/packages/backend/src/core/activitypub/type.ts b/packages/backend/src/core/activitypub/type.ts
index 16812b7a4..aa1d7c306 100644
--- a/packages/backend/src/core/activitypub/type.ts
+++ b/packages/backend/src/core/activitypub/type.ts
@@ -11,6 +11,7 @@ export interface IObject {
 	type: string | string[];
 	id?: string;
 	name?: string | null;
+	contentMap?: Record<string, string | null>;
 	summary?: string;
 	_misskey_summary?: string;
 	published?: string;
@@ -122,6 +123,7 @@ export interface IPost extends IObject {
 	type: 'Note' | 'Question' | 'Article' | 'Audio' | 'Document' | 'Image' | 'Page' | 'Video' | 'Event';
 	source?: {
 		content: string;
+		contentMap?: Record<string, string | null>;
 		mediaType: string;
 	};
 	_misskey_quote?: string;
@@ -134,6 +136,7 @@ export interface IQuestion extends IObject {
 	actor: string;
 	source?: {
 		content: string;
+		contentMap?: Record<string, string | null>;
 		mediaType: string;
 	};
 	_misskey_quote?: string;
diff --git a/packages/backend/src/core/entities/NoteEntityService.ts b/packages/backend/src/core/entities/NoteEntityService.ts
index f111b6540..b1526d468 100644
--- a/packages/backend/src/core/entities/NoteEntityService.ts
+++ b/packages/backend/src/core/entities/NoteEntityService.ts
@@ -331,6 +331,7 @@ export class NoteEntityService implements OnModuleInit {
 			userId: note.userId,
 			user: this.userEntityService.pack(note.user ?? note.userId, me),
 			text: text,
+			lang: note.lang,
 			cw: note.cw,
 			visibility: note.visibility,
 			localOnly: note.localOnly,
diff --git a/packages/backend/src/misc/langmap.ts b/packages/backend/src/misc/langmap.ts
index 5ff933865..4e9c2f69a 100644
--- a/packages/backend/src/misc/langmap.ts
+++ b/packages/backend/src/misc/langmap.ts
@@ -669,3 +669,631 @@ export const langmap = {
 		nativeName: 'isiZulu',
 	},
 };
+
+
+export const ISO_639_1 = {
+  aa: {
+    nativeName: 'Afaraf',
+  },
+  ab: {
+    nativeName: 'аҧсуа бызшәа',
+  },
+  ae: {
+    nativeName: 'avesta',
+  },
+  af: {
+    nativeName: 'Afrikaans',
+  },
+  ak: {
+    nativeName: 'Akan',
+  },
+  am: {
+    nativeName: 'አማርኛ',
+  },
+  an: {
+    nativeName: 'aragonés',
+  },
+  ar: {
+    nativeName: 'اللغة العربية',
+  },
+  as: {
+    nativeName: 'অসমীয়া',
+  },
+  av: {
+    nativeName: 'авар мацӀ',
+  },
+  ay: {
+    nativeName: 'aymar aru',
+  },
+  az: {
+    nativeName: 'azərbaycan dili',
+  },
+  ba: {
+    nativeName: 'башҡорт теле',
+  },
+  be: {
+    nativeName: 'беларуская мова',
+  },
+  bg: {
+    nativeName: 'български език',
+  },
+  bh: {
+    nativeName: 'भोजपुरी',
+  },
+  bi: {
+    nativeName: 'Bislama',
+  },
+  bm: {
+    nativeName: 'bamanankan',
+  },
+  bn: {
+    nativeName: 'বাংলা',
+  },
+  bo: {
+    nativeName: 'བོད་ཡིག',
+  },
+  br: {
+    nativeName: 'brezhoneg',
+  },
+  bs: {
+    nativeName: 'bosanski jezik',
+  },
+  ca: {
+    nativeName: 'Català',
+  },
+  ce: {
+    nativeName: 'нохчийн мотт',
+  },
+  ch: {
+    nativeName: 'Chamoru',
+  },
+  co: {
+    nativeName: 'corsu',
+  },
+  cr: {
+    nativeName: 'ᓀᐦᐃᔭᐍᐏᐣ',
+  },
+  cs: {
+    nativeName: 'čeština',
+  },
+  cu: {
+    nativeName: 'ѩзыкъ словѣньскъ',
+  },
+  cv: {
+    nativeName: 'чӑваш чӗлхи',
+  },
+  cy: {
+    nativeName: 'Cymraeg',
+  },
+  da: {
+    nativeName: 'dansk',
+  },
+  de: {
+    nativeName: 'Deutsch',
+  },
+  dv: {
+    nativeName: 'Dhivehi',
+  },
+  dz: {
+    nativeName: 'རྫོང་ཁ',
+  },
+  ee: {
+    nativeName: 'Eʋegbe',
+  },
+  el: {
+    nativeName: 'Ελληνικά',
+  },
+  en: {
+    nativeName: 'English',
+  },
+  eo: {
+    nativeName: 'Esperanto',
+  },
+  es: {
+    nativeName: 'Español',
+  },
+  et: {
+    nativeName: 'eesti',
+  },
+  eu: {
+    nativeName: 'euskara',
+  },
+  fa: {
+    nativeName: 'فارسی',
+  },
+  ff: {
+    nativeName: 'Fulfulde',
+  },
+  fi: {
+    nativeName: 'suomi',
+  },
+  fj: {
+    nativeName: 'Vakaviti',
+  },
+  fo: {
+    nativeName: 'føroyskt',
+  },
+  fr: {
+    nativeName: 'Français',
+  },
+  fy: {
+    nativeName: 'Frysk',
+  },
+  ga: {
+    nativeName: 'Gaeilge',
+  },
+  gd: {
+    nativeName: 'Gàidhlig',
+  },
+  gl: {
+    nativeName: 'galego',
+  },
+  gu: {
+    nativeName: 'ગુજરાતી',
+  },
+  gv: {
+    nativeName: 'Gaelg',
+  },
+  ha: {
+    nativeName: 'هَوُسَ',
+  },
+  he: {
+    nativeName: 'עברית',
+  },
+  hi: {
+    nativeName: 'हिन्दी',
+  },
+  ho: {
+    nativeName: 'Hiri Motu',
+  },
+  hr: {
+    nativeName: 'Hrvatski',
+  },
+  ht: {
+    nativeName: 'Kreyòl ayisyen',
+  },
+  hu: {
+    nativeName: 'magyar',
+  },
+  hy: {
+    nativeName: 'Հայերեն',
+  },
+  hz: {
+    nativeName: 'Otjiherero',
+  },
+  ia: {
+    nativeName: 'Interlingua',
+  },
+  id: {
+    nativeName: 'Bahasa Indonesia',
+  },
+  ie: {
+    nativeName: 'Interlingue',
+  },
+  ig: {
+    nativeName: 'Asụsụ Igbo',
+  },
+  ii: {
+    nativeName: 'ꆈꌠ꒿ Nuosuhxop',
+  },
+  ik: {
+    nativeName: 'Iñupiaq',
+  },
+  io: {
+    nativeName: 'Ido',
+  },
+  is: {
+    nativeName: 'Íslenska',
+  },
+  it: {
+    nativeName: 'Italiano',
+  },
+  iu: {
+    nativeName: 'ᐃᓄᒃᑎᑐᑦ',
+  },
+  ja: {
+    nativeName: '日本語',
+  },
+  jv: {
+    nativeName: 'basa Jawa',
+  },
+  ka: {
+    nativeName: 'ქართული',
+  },
+  kg: {
+    nativeName: 'Kikongo',
+  },
+  ki: {
+    nativeName: 'Gĩkũyũ',
+  },
+  kj: {
+    nativeName: 'Kuanyama',
+  },
+  kk: {
+    nativeName: 'қазақ тілі',
+  },
+  kl: {
+    nativeName: 'kalaallisut',
+  },
+  km: {
+    nativeName: 'ខេមរភាសា',
+  },
+  kn: {
+    nativeName: 'ಕನ್ನಡ',
+  },
+  ko: {
+    nativeName: '한국어',
+  },
+  kr: {
+    nativeName: 'Kanuri',
+  },
+  ks: {
+    nativeName: 'कश्मीरी',
+  },
+  ku: {
+    nativeName: 'Kurmancî',
+  },
+  kv: {
+    nativeName: 'коми кыв',
+  },
+  kw: {
+    nativeName: 'Kernewek',
+  },
+  ky: {
+    nativeName: 'Кыргызча',
+  },
+  la: {
+    nativeName: 'latine',
+  },
+  lb: {
+    nativeName: 'Lëtzebuergesch',
+  },
+  lg: {
+    nativeName: 'Luganda',
+  },
+  li: {
+    nativeName: 'Limburgs',
+  },
+  ln: {
+    nativeName: 'Lingála',
+  },
+  lo: {
+    nativeName: 'ລາວ',
+  },
+  lt: {
+    nativeName: 'lietuvių kalba',
+  },
+  lu: {
+    nativeName: 'Tshiluba',
+  },
+  lv: {
+    nativeName: 'latviešu valoda',
+  },
+  mg: {
+    nativeName: 'fiteny malagasy',
+  },
+  mh: {
+    nativeName: 'Kajin M̧ajeļ',
+  },
+  mi: {
+    nativeName: 'te reo Māori',
+  },
+  mk: {
+    nativeName: 'македонски јазик',
+  },
+  ml: {
+    nativeName: 'മലയാളം',
+  },
+  mn: {
+    nativeName: 'Монгол хэл',
+  },
+  mr: {
+    nativeName: 'मराठी',
+  },
+  ms: {
+    nativeName: 'Bahasa Melayu',
+  },
+  'ms-Arab': {
+    nativeName: 'بهاس ملايو',
+  },
+  mt: {
+    nativeName: 'Malti',
+  },
+  my: {
+    nativeName: 'ဗမာစာ',
+  },
+  na: {
+    nativeName: 'Ekakairũ Naoero',
+  },
+  nb: {
+    nativeName: 'Norsk bokmål',
+  },
+  nd: {
+    nativeName: 'isiNdebele',
+  },
+  ne: {
+    nativeName: 'नेपाली',
+  },
+  ng: {
+    nativeName: 'Owambo',
+  },
+  nl: {
+    nativeName: 'Nederlands',
+  },
+  nn: {
+    nativeName: 'Norsk Nynorsk',
+  },
+  no: {
+    nativeName: 'Norsk',
+  },
+  nr: {
+    nativeName: 'isiNdebele',
+  },
+  nv: {
+    nativeName: 'Diné bizaad',
+  },
+  ny: {
+    nativeName: 'chiCheŵa',
+  },
+  oc: {
+    nativeName: 'occitan',
+  },
+  oj: {
+    nativeName: 'ᐊᓂᔑᓈᐯᒧᐎᓐ',
+  },
+  om: {
+    nativeName: 'Afaan Oromoo',
+  },
+  or: {
+    nativeName: 'ଓଡ଼ିଆ',
+  },
+  os: {
+    nativeName: 'ирон æвзаг',
+  },
+  pa: {
+    nativeName: 'ਪੰਜਾਬੀ',
+  },
+  pi: {
+    nativeName: 'पाऴि',
+  },
+  pl: {
+    nativeName: 'Polski',
+  },
+  ps: {
+    nativeName: 'پښتو',
+  },
+  pt: {
+    nativeName: 'Português',
+  },
+  qu: {
+    nativeName: 'Runa Simi',
+  },
+  rm: {
+    nativeName: 'rumantsch grischun',
+  },
+  rn: {
+    nativeName: 'Ikirundi',
+  },
+  ro: {
+    nativeName: 'Română',
+  },
+  ru: {
+    nativeName: 'Русский',
+  },
+  rw: {
+    nativeName: 'Ikinyarwanda',
+  },
+  sa: {
+    nativeName: 'संस्कृतम्',
+  },
+  sc: {
+    nativeName: 'sardu',
+  },
+  sd: {
+    nativeName: 'सिन्धी',
+  },
+  se: {
+    nativeName: 'Davvisámegiella',
+  },
+  sg: {
+    nativeName: 'yângâ tî sängö',
+  },
+  si: {
+    nativeName: 'සිංහල',
+  },
+  sk: {
+    nativeName: 'slovenčina',
+  },
+  sl: {
+    nativeName: 'slovenščina',
+  },
+  sn: {
+    nativeName: 'chiShona',
+  },
+  so: {
+    nativeName: 'Soomaaliga',
+  },
+  sq: {
+    nativeName: 'Shqip',
+  },
+  sr: {
+    nativeName: 'српски језик',
+  },
+  ss: {
+    nativeName: 'SiSwati',
+  },
+  st: {
+    nativeName: 'Sesotho',
+  },
+  su: {
+    nativeName: 'Basa Sunda',
+  },
+  sv: {
+    nativeName: 'Svenska',
+  },
+  sw: {
+    nativeName: 'Kiswahili',
+  },
+  ta: {
+    nativeName: 'தமிழ்',
+  },
+  te: {
+    nativeName: 'తెలుగు',
+  },
+  tg: {
+    nativeName: 'тоҷикӣ',
+  },
+  th: {
+    nativeName: 'ไทย',
+  },
+  ti: {
+    nativeName: 'ትግርኛ',
+  },
+  tk: {
+    nativeName: 'Türkmen',
+  },
+  tl: {
+    nativeName: 'Tagalog',
+  },
+  tn: {
+    nativeName: 'Setswana',
+  },
+  to: {
+    nativeName: 'faka Tonga',
+  },
+  tr: {
+    nativeName: 'Türkçe',
+  },
+  ts: {
+    nativeName: 'Xitsonga',
+  },
+  tt: {
+    nativeName: 'татар теле',
+  },
+  tw: {
+    nativeName: 'Twi',
+  },
+  ty: {
+    nativeName: 'Reo Tahiti',
+  },
+  ug: {
+    nativeName: 'ئۇيغۇرچە‎',
+  },
+  uk: {
+    nativeName: 'Українська',
+  },
+  ur: {
+    nativeName: 'اردو',
+  },
+  vi: {
+    nativeName: 'Tiếng Việt',
+  },
+  vo: {
+    nativeName: 'Volapük',
+  },
+  wa: {
+    nativeName: 'Walon',
+  },
+  wo: {
+    nativeName: 'Wollof',
+  },
+  xh: {
+    nativeName: 'isiXhosa',
+  },
+  yi: {
+    nativeName: 'ייִדיש',
+  },
+  zu: {
+    nativeName: 'isiZulu',
+  },
+};
+
+export const ISO_639_3 = {
+  ast: {
+    nativeName: 'Asturianu',
+  },
+  chr: {
+    nativeName: 'ᏣᎳᎩ ᎦᏬᏂᎯᏍᏗ',
+  },
+  ckb: {
+    nativeName: 'سۆرانی',
+  },
+  cnr: {
+    nativeName: 'crnogorski',
+  },
+  csb: {
+    nativeName: 'Kaszëbsczi',
+  },
+  gsw: {
+    nativeName: 'Schwiizertütsch',
+  },
+  jbo: {
+    nativeName: 'la .lojban.',
+  },
+  kab: {
+    nativeName: 'Taqbaylit',
+  },
+  ldn: {
+    nativeName: 'Láadan',
+  },
+  lfn: {
+    nativeName: 'lingua franca nova',
+  },
+  moh: {
+    nativeName: 'Kanienʼkéha',
+  },
+  nds: {
+    nativeName: 'Plattdüütsch',
+  },
+  pdc: {
+    nativeName: 'Pennsilfaani-Deitsch',
+  },
+  sco: {
+    nativeName: 'Scots',
+  },
+  sma: {
+    nativeName: 'Åarjelsaemien Gïele',
+  },
+  smj: {
+    nativeName: 'Julevsámegiella',
+  },
+  szl: {
+    nativeName: 'ślůnsko godka',
+  },
+  tok: {
+    nativeName: 'toki pona',
+  },
+  vai: {
+    nativeName: 'ꕙꔤ',
+  },
+  xal: {
+    nativeName: 'Хальмг келн',
+  },
+  zba: {
+    nativeName: 'باليبلن',
+  },
+  zgh: {
+    nativeName: 'ⵜⴰⵎⴰⵣⵉⵖⵜ',
+  },
+};
+
+export const ISO_639_1_REGIONAL = {
+  'zh-CN': {
+    nativeName: '简体中文',
+  },
+  'zh-HK': {
+    nativeName: '繁體中文（香港）',
+  },
+  'zh-TW': {
+    nativeName: '繁體中文（臺灣）',
+  },
+  'zh-YUE': {
+    nativeName: '廣東話',
+  },
+};
+
+export const SUPPORTED_POST_LOCALES = {
+	...ISO_639_1,
+  ...ISO_639_3,
+  ...ISO_639_1_REGIONAL,
+};
diff --git a/packages/backend/src/models/Note.ts b/packages/backend/src/models/Note.ts
index 7803a68c7..0b2d3169d 100644
--- a/packages/backend/src/models/Note.ts
+++ b/packages/backend/src/models/Note.ts
@@ -66,6 +66,12 @@ export class MiNote {
 	})
 	public text: string | null;
 
+	@Column('varchar', {
+		length: 10,
+		nullable: true,
+	})
+	public lang: string | null;
+
 	@Column('varchar', {
 		length: 256, nullable: true,
 	})
diff --git a/packages/backend/src/models/json-schema/note.ts b/packages/backend/src/models/json-schema/note.ts
index 2641161c8..aead839e2 100644
--- a/packages/backend/src/models/json-schema/note.ts
+++ b/packages/backend/src/models/json-schema/note.ts
@@ -2,6 +2,7 @@
  * SPDX-FileCopyrightText: syuilo and misskey-project
  * SPDX-License-Identifier: AGPL-3.0-only
  */
+import { SUPPORTED_POST_LOCALES } from "@/misc/langmap.js";
 
 export const packedNoteSchema = {
 	type: 'object',
@@ -26,6 +27,11 @@ export const packedNoteSchema = {
 			type: 'string',
 			optional: false, nullable: true,
 		},
+		lang: {
+			type: 'string',
+			enum: [...Object.keys(SUPPORTED_POST_LOCALES)],
+			nullable: true,
+		},
 		cw: {
 			type: 'string',
 			optional: true, nullable: true,
diff --git a/packages/backend/src/queue/processors/ExportNotesProcessorService.ts b/packages/backend/src/queue/processors/ExportNotesProcessorService.ts
index b45d4165c..4c530ac32 100644
--- a/packages/backend/src/queue/processors/ExportNotesProcessorService.ts
+++ b/packages/backend/src/queue/processors/ExportNotesProcessorService.ts
@@ -45,6 +45,7 @@ class NoteStream extends ReadableStream<Record<string, unknown>> {
 			return {
 				id: note.id,
 				text: note.text,
+				lang: note.lang,
 				createdAt: idService.parse(note.id).date.toISOString(),
 				fileIds: note.fileIds,
 				files: files,
diff --git a/packages/backend/src/server/api/endpoints/i/update.ts b/packages/backend/src/server/api/endpoints/i/update.ts
index eb537a59d..3341ede75 100644
--- a/packages/backend/src/server/api/endpoints/i/update.ts
+++ b/packages/backend/src/server/api/endpoints/i/update.ts
@@ -16,7 +16,7 @@ import type { MiLocalUser, MiUser } from '@/models/User.js';
 import { birthdaySchema, descriptionSchema, locationSchema, nameSchema } from '@/models/User.js';
 import type { MiUserProfile } from '@/models/UserProfile.js';
 import { normalizeForSearch } from '@/misc/normalize-for-search.js';
-import { langmap } from '@/misc/langmap.js';
+import { SUPPORTED_POST_LOCALES } from '@/misc/langmap.js';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
 import { GlobalEventService } from '@/core/GlobalEventService.js';
@@ -150,7 +150,7 @@ export const paramDef = {
 		description: { ...descriptionSchema, nullable: true },
 		location: { ...locationSchema, nullable: true },
 		birthday: { ...birthdaySchema, nullable: true },
-		lang: { type: 'string', enum: [null, ...Object.keys(langmap)] as string[], nullable: true },
+		lang: { type: 'string', enum: [null, ...Object.keys(SUPPORTED_POST_LOCALES)] as string[], nullable: true },
 		avatarId: { type: 'string', format: 'misskey:id', nullable: true },
 		avatarDecorations: { type: 'array', maxItems: 16, items: {
 			type: 'object',
diff --git a/packages/backend/src/server/api/endpoints/notes/create.ts b/packages/backend/src/server/api/endpoints/notes/create.ts
index ddccbdae5..a85aa0fa4 100644
--- a/packages/backend/src/server/api/endpoints/notes/create.ts
+++ b/packages/backend/src/server/api/endpoints/notes/create.ts
@@ -23,6 +23,7 @@ import { isQuote, isRenote } from '@/misc/is-renote.js';
 import { IdentifiableError } from '@/misc/identifiable-error.js';
 import { LoggerService } from '@/core/LoggerService.js';
 import { ApiError } from '../../error.js';
+import { SUPPORTED_POST_LOCALES } from "@/misc/langmap.js";
 
 export const meta = {
 	tags: ['notes'],
@@ -210,6 +211,11 @@ export const paramDef = {
 			maxLength: MAX_NOTE_TEXT_LENGTH,
 			nullable: true,
 		},
+		lang: {
+			type: "string",
+			enum: Object.keys(SUPPORTED_POST_LOCALES),
+			nullable: true,
+		},
 		fileIds: {
 			type: 'array',
 			uniqueItems: true,
@@ -484,6 +490,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 						expiresAt: ps.poll.expiresAt ? new Date(ps.poll.expiresAt) : null,
 					} : undefined,
 					text: ps.text ?? undefined,
+					lang: ps.lang,
 					reply,
 					renote,
 					cw: ps.cw,
diff --git a/packages/backend/src/types.ts b/packages/backend/src/types.ts
index dc13af42f..00c8dcace 100644
--- a/packages/backend/src/types.ts
+++ b/packages/backend/src/types.ts
@@ -375,6 +375,7 @@ export type NoteCreateOption = {
 	scheduledAt?: Date | null;
 	name?: string | null;
 	text?: string | null;
+	lang?: string | null;
 	reply?: MiNote | null;
 	renote?: MiNote | null;
 	files?: MiDriveFile[] | null;
diff --git a/packages/frontend/src/components/MkMenu.vue b/packages/frontend/src/components/MkMenu.vue
index d91239b9e..8decb8f2d 100644
--- a/packages/frontend/src/components/MkMenu.vue
+++ b/packages/frontend/src/components/MkMenu.vue
@@ -12,8 +12,15 @@ SPDX-License-Identifier: AGPL-3.0-only
 		:style="{ width: (width && !asDrawer) ? width + 'px' : '', maxHeight: maxHeight ? maxHeight + 'px' : '' }"
 		@contextmenu.self="e => e.preventDefault()"
 	>
+  	<div v-if="search" style="padding: 5px 6px;">
+  		<MkInput v-model="searchbar" autofocus>
+  			<template #prefix><i class="ti ti-search"></i></template>
+			</MkInput>
+  	</div>
 		<template v-for="(item, i) in (items2 ?? [])">
-			<div v-if="item.type === 'divider'" role="separator" :class="$style.divider"></div>
+			<div v-if="item.type === 'divider'" role="separator" :class="$style.divider">
+				<span v-if="item.text" style="opacity: 0.7; font-size: smaller;">{{ item.text }}</span>
+			</div>
 			<span v-else-if="item.type === 'label'" role="menuitem" :class="[$style.label, $style.item]">
 				<span style="opacity: 0.7;">{{ item.text }}</span>
 			</span>
@@ -103,6 +110,7 @@ const childrenCache = new WeakMap<MenuParent, MenuItem[]>();
 </script>
 
 <script lang="ts" setup>
+import MkInput from "@/components/MkInput.vue";
 const XChild = defineAsyncComponent(() => import('./MkMenu.child.vue'));
 
 const props = defineProps<{
@@ -112,6 +120,7 @@ const props = defineProps<{
 	align?: 'center' | string;
 	width?: number;
 	maxHeight?: number;
+	search?: boolean;
 }>();
 
 const emit = defineEmits<{
@@ -119,6 +128,8 @@ const emit = defineEmits<{
 	(ev: 'hide'): void;
 }>();
 
+const searchbar = ref<string | null>('');
+
 const itemsEl = shallowRef<HTMLDivElement>();
 
 const items2 = ref<InnerMenuItem[]>();
@@ -135,24 +146,38 @@ const childShowingItem = ref<MenuItem | null>();
 
 let preferClick = isTouchUsing || props.asDrawer;
 
-watch(() => props.items, () => {
-	const items = [...props.items].filter(item => item !== undefined) as (NonNullable<MenuItem> | MenuPending)[];
+const filteredItems = ref<InnerMenuItem[]>([]);
 
-	for (let i = 0; i < items.length; i++) {
-		const item = items[i];
+watch(
+  () => [props.items, searchbar.value],
+  () => {
+    let items = [...props.items].filter(item => item !== undefined) as (NonNullable<MenuItem> | MenuPending)[];
 
-		if ('then' in item) { // if item is Promise
-			items[i] = { type: 'pending' };
-			item.then(actualItem => {
-				if (items2.value?.[i]) items2.value[i] = actualItem;
-			});
-		}
-	}
+    for (let i = 0; i < items.length; i++) {
+      const item = items[i];
+
+      if ('then' in item) { // if item is a Promise
+        items[i] = { type: 'pending' };
+        item.then(actualItem => {
+          if (items2.value?.[i]) items2.value[i] = actualItem;
+        });
+      }
+    }
+
+    // Apply the search filter
+    filteredItems.value = items.filter(item => {
+      // Modify the condition based on your data structure
+      if ('text' in item) {
+        return item.text.toLowerCase().includes(searchbar.value.toLowerCase());
+      }
+      return true;
+    }) as InnerMenuItem[];
+		// console.log(filteredItems.value)
+    items2.value = filteredItems.value;
+  },
+  { immediate: true }
+);
 
-	items2.value = items as InnerMenuItem[];
-}, {
-	immediate: true,
-});
 
 const childMenu = ref<MenuItem[] | null>();
 const childTarget = shallowRef<HTMLElement | null>();
@@ -511,8 +536,8 @@ onBeforeUnmount(() => {
 }
 
 .divider {
-	margin: 8px 0;
-	border-top: solid 0.5px var(--divider);
+	margin: 8px 8px;
+	border-bottom: solid 0.5px var(--divider);
 }
 
 .radio {
diff --git a/packages/frontend/src/components/MkPopupMenu.vue b/packages/frontend/src/components/MkPopupMenu.vue
index be0b07612..5084e908b 100644
--- a/packages/frontend/src/components/MkPopupMenu.vue
+++ b/packages/frontend/src/components/MkPopupMenu.vue
@@ -5,7 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <template>
 <MkModal ref="modal" v-slot="{ type, maxHeight }" :manualShowing="manualShowing" :zPriority="'high'" :src="src" :transparentBg="true" @click="click" @close="onModalClose" @closed="onModalClosed">
-	<MkMenu :items="items" :align="align" :width="width" :max-height="maxHeight" :asDrawer="type === 'drawer'" :class="{ [$style.drawer]: type === 'drawer' }" @close="onMenuClose" @hide="hide"/>
+	<MkMenu :items="items" :align="align" :width="width" :max-height="maxHeight" :asDrawer="type === 'drawer'" :search="search" :class="{ [$style.drawer]: type === 'drawer' }" @close="onMenuClose" @hide="hide"/>
 </MkModal>
 </template>
 
@@ -21,6 +21,7 @@ defineProps<{
 	width?: number;
 	viaKeyboard?: boolean;
 	src?: any;
+	search?: boolean;
 }>();
 
 const emit = defineEmits<{
diff --git a/packages/frontend/src/components/MkPostForm.vue b/packages/frontend/src/components/MkPostForm.vue
index 66512f730..0db8ce631 100644
--- a/packages/frontend/src/components/MkPostForm.vue
+++ b/packages/frontend/src/components/MkPostForm.vue
@@ -41,6 +41,22 @@ SPDX-License-Identifier: AGPL-3.0-only
 				<span v-else-if="reactionAcceptance === 'likeOnlyForRemote'"><i class="ti ti-heart-plus"></i></span>
 				<span v-else><i class="ti ti-icons"></i></span>
 			</button>
+			<button
+			 	v-click-anime
+				ref="languageButton"
+				v-tooltip="i18n.ts.language"
+				class="_button"
+				:class="[$style.headerRightItem]"
+				@click="setLanguage"
+			>
+				<i
+					v-if="language === '' || language == null"
+					class="ti ti-language"
+				></i>
+				<span v-else style="font-weight: bold">
+					{{ language.split("-")[0] }}
+				</span>
+			</button>
 			<button v-if="!props.instant" v-click-anime v-tooltip="i18n.ts.drafts" class="_button" :class="$style.headerRightItem" @click="openDrafts">
 				<i class="ti ti-pencil"></i>
 			</button>
@@ -158,6 +174,7 @@ import { miLocalStorage } from '@/local-storage.js';
 import { dateTimeFormat } from '@/scripts/intl-const.js';
 import { claimAchievement } from '@/scripts/achievements.js';
 import { mfmFunctionPicker } from '@/scripts/mfm-function-picker.js';
+import { SUPPORTED_POST_LOCALES } from "@/scripts/langmap";
 
 const $i = signinRequired();
 
@@ -205,6 +222,7 @@ const textareaEl = shallowRef<HTMLTextAreaElement | null>(null);
 const cwInputEl = shallowRef<HTMLInputElement | null>(null);
 const hashtagsInputEl = shallowRef<HTMLInputElement | null>(null);
 const visibilityButton = shallowRef<HTMLElement>();
+const languageButton = shallowRef<HTMLElement | null>(null);
 
 const posting = ref(false);
 const posted = ref(false);
@@ -243,6 +261,12 @@ const imeText = ref('');
 const showingOptions = ref(false);
 const textAreaReadOnly = ref(false);
 
+let language = ref<string | null>(
+	props.initialLanguage ??
+		defaultStore.state.recentlyUsedPostLanguages[0] ??
+		localStorage.getItem("lang")?.split("-")[0],
+);
+
 const draftKey = computed((): string => {
 	let key = channel.value ? `channel:${channel.value.id}` : '';
 
@@ -591,6 +615,69 @@ async function toggleReactionAcceptance() {
 	reactionAcceptance.value = select.result;
 }
 
+function setLanguage() {
+	const langs = Object.keys(SUPPORTED_POST_LOCALES);
+	const recentlyUsed = defaultStore.state.recentlyUsedPostLanguages;
+
+	const actions: Array<MenuItem | null> = [
+		{ type: 'divider', text: 'Recent Languages' },
+		// Current language
+		language.value
+			? {
+				text: SUPPORTED_POST_LOCALES[language.value].nativeName,
+				danger: false,
+				active: true,
+				action: () => {},
+			}
+			: null,
+
+		// Recently used languages (excluding current)
+		...recentlyUsed
+			.filter(lang => lang !== language.value && langs.includes(lang))
+			.map(lang => ({
+				text: SUPPORTED_POST_LOCALES[lang].nativeName,
+				danger: false,
+				active: false,
+				action: () => {
+					language.value = lang;
+				},
+			})),
+
+		// Separator if there are recently used languages
+		recentlyUsed.some(lang => lang !== language.value && langs.includes(lang))
+			? { type: 'divider' }
+			: null,
+
+		{
+			text: 'No Language',
+			danger: false,
+			active: false,
+			action: () => {
+				language.value = null;
+			},
+		},
+
+		// All other languages not in recently used and not the current language
+		...langs
+			.filter(
+				lang => lang !== language.value && !recentlyUsed.includes(lang)
+			)
+			.map(lang => ({
+				text: SUPPORTED_POST_LOCALES[lang].nativeName,
+				danger: false,
+				active: false,
+				action: () => {
+					language.value = lang;
+				},
+			})),
+	].filter(Boolean); // Remove null values
+
+	if (languageButton) {
+		os.popupMenu(actions, languageButton, { search: true });
+	}
+}
+
+
 function pushVisibleUser(user: Misskey.entities.UserDetailed) {
 	if (!visibleUsers.value.some(u => u.username === user.username && u.host === user.host)) {
 		visibleUsers.value.push(user);
@@ -772,6 +859,7 @@ function saveDraft() {
 		} : undefined,
 		data: {
 			text: text.value,
+			lang: language.value,
 			useCw: useCw.value,
 			cw: cw.value,
 			visibility: visibility.value,
@@ -843,6 +931,7 @@ function loadDraft(exactMatch = false) {
 			scheduledTime.value = null;
 		}
 		text.value = draft.value.data.text ?? '';
+		language.value = draft.value.data.language ?? '';
 		useCw.value = draft.value.data.useCw;
 		cw.value = draft.value.data.cw;
 		visibility.value = draft.value.data.visibility;
@@ -940,6 +1029,7 @@ async function post(ev?: MouseEvent) {
 
 	let postData = {
 		text: text.value === '' ? null : text.value,
+		lang: language.value ?? undefined,
 		// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
 		fileIds: files.value.length > 0 ? files.value.filter(f => f?.id).map(f => f.id) : undefined,
 		replyId: reply.value ? reply.value.id : undefined,
@@ -1048,6 +1138,27 @@ async function post(ev?: MouseEvent) {
 				claimAchievement('postedAt0min0sec');
 			}
 		});
+
+		if (language.value) {
+    	const languages = Object.keys(SUPPORTED_POST_LOCALES);
+    	const maxLength = 6;
+
+    	defaultStore.set(
+    		"recentlyUsedPostLanguages",
+    		[language.value]
+    			.concat(
+    				defaultStore.state.recentlyUsedPostLanguages.filter(
+    					(lang) => {
+    						return (
+    							lang !== language.value &&
+    							languages.includes(lang)
+    						);
+    					},
+    				),
+    			)
+    			.slice(0, maxLength),
+    	);
+    }
 	}).catch(err => {
 		posting.value = false;
 		os.alert({
@@ -1144,6 +1255,7 @@ onMounted(() => {
 		if (props.initialNote) {
 			const init = props.initialNote;
 			text.value = init.text ? init.text : '';
+			language.value = init.lang;
 			// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
 			files.value = init.files?.filter(f => f?.id && f.type && f.name) ?? [];
 			cw.value = init.cw ?? null;
diff --git a/packages/frontend/src/components/MkPostFormDialog.vue b/packages/frontend/src/components/MkPostFormDialog.vue
index 9533846f7..4a3dc18f8 100644
--- a/packages/frontend/src/components/MkPostFormDialog.vue
+++ b/packages/frontend/src/components/MkPostFormDialog.vue
@@ -25,6 +25,7 @@ const props = withDefaults(defineProps<{
 	initialText?: string;
 	initialCw?: string;
 	initialVisibility?: (typeof Misskey.noteVisibilities)[number];
+	initialLanguage?: typeof misskey.languages;
 	initialFiles?: Misskey.entities.DriveFile[];
 	initialLocalOnly?: boolean;
 	initialVisibleUsers?: Misskey.entities.UserDetailed[];
diff --git a/packages/frontend/src/os.ts b/packages/frontend/src/os.ts
index 5a1071a92..d1b265aab 100644
--- a/packages/frontend/src/os.ts
+++ b/packages/frontend/src/os.ts
@@ -708,6 +708,7 @@ export function popupMenu(items: MenuItem[], src?: HTMLElement | EventTarget | n
 	width?: number;
 	viaKeyboard?: boolean;
 	onClosing?: () => void;
+	search: boolean;
 }): Promise<void> {
 	return new Promise(resolve => {
 		let dispose;
@@ -717,6 +718,7 @@ export function popupMenu(items: MenuItem[], src?: HTMLElement | EventTarget | n
 			width: options?.width,
 			align: options?.align,
 			viaKeyboard: options?.viaKeyboard,
+			search: options?.search,
 		}, {
 			closed: () => {
 				resolve();
diff --git a/packages/frontend/src/scripts/langmap.ts b/packages/frontend/src/scripts/langmap.ts
index b32de1596..70360df36 100644
--- a/packages/frontend/src/scripts/langmap.ts
+++ b/packages/frontend/src/scripts/langmap.ts
@@ -669,3 +669,631 @@ export const langmap = {
 		nativeName: 'isiZulu',
 	},
 };
+
+
+export const ISO_639_1 = {
+  aa: {
+    nativeName: 'Afaraf',
+  },
+  ab: {
+    nativeName: 'аҧсуа бызшәа',
+  },
+  ae: {
+    nativeName: 'avesta',
+  },
+  af: {
+    nativeName: 'Afrikaans',
+  },
+  ak: {
+    nativeName: 'Akan',
+  },
+  am: {
+    nativeName: 'አማርኛ',
+  },
+  an: {
+    nativeName: 'aragonés',
+  },
+  ar: {
+    nativeName: 'اللغة العربية',
+  },
+  as: {
+    nativeName: 'অসমীয়া',
+  },
+  av: {
+    nativeName: 'авар мацӀ',
+  },
+  ay: {
+    nativeName: 'aymar aru',
+  },
+  az: {
+    nativeName: 'azərbaycan dili',
+  },
+  ba: {
+    nativeName: 'башҡорт теле',
+  },
+  be: {
+    nativeName: 'беларуская мова',
+  },
+  bg: {
+    nativeName: 'български език',
+  },
+  bh: {
+    nativeName: 'भोजपुरी',
+  },
+  bi: {
+    nativeName: 'Bislama',
+  },
+  bm: {
+    nativeName: 'bamanankan',
+  },
+  bn: {
+    nativeName: 'বাংলা',
+  },
+  bo: {
+    nativeName: 'བོད་ཡིག',
+  },
+  br: {
+    nativeName: 'brezhoneg',
+  },
+  bs: {
+    nativeName: 'bosanski jezik',
+  },
+  ca: {
+    nativeName: 'Català',
+  },
+  ce: {
+    nativeName: 'нохчийн мотт',
+  },
+  ch: {
+    nativeName: 'Chamoru',
+  },
+  co: {
+    nativeName: 'corsu',
+  },
+  cr: {
+    nativeName: 'ᓀᐦᐃᔭᐍᐏᐣ',
+  },
+  cs: {
+    nativeName: 'čeština',
+  },
+  cu: {
+    nativeName: 'ѩзыкъ словѣньскъ',
+  },
+  cv: {
+    nativeName: 'чӑваш чӗлхи',
+  },
+  cy: {
+    nativeName: 'Cymraeg',
+  },
+  da: {
+    nativeName: 'dansk',
+  },
+  de: {
+    nativeName: 'Deutsch',
+  },
+  dv: {
+    nativeName: 'Dhivehi',
+  },
+  dz: {
+    nativeName: 'རྫོང་ཁ',
+  },
+  ee: {
+    nativeName: 'Eʋegbe',
+  },
+  el: {
+    nativeName: 'Ελληνικά',
+  },
+  en: {
+    nativeName: 'English',
+  },
+  eo: {
+    nativeName: 'Esperanto',
+  },
+  es: {
+    nativeName: 'Español',
+  },
+  et: {
+    nativeName: 'eesti',
+  },
+  eu: {
+    nativeName: 'euskara',
+  },
+  fa: {
+    nativeName: 'فارسی',
+  },
+  ff: {
+    nativeName: 'Fulfulde',
+  },
+  fi: {
+    nativeName: 'suomi',
+  },
+  fj: {
+    nativeName: 'Vakaviti',
+  },
+  fo: {
+    nativeName: 'føroyskt',
+  },
+  fr: {
+    nativeName: 'Français',
+  },
+  fy: {
+    nativeName: 'Frysk',
+  },
+  ga: {
+    nativeName: 'Gaeilge',
+  },
+  gd: {
+    nativeName: 'Gàidhlig',
+  },
+  gl: {
+    nativeName: 'galego',
+  },
+  gu: {
+    nativeName: 'ગુજરાતી',
+  },
+  gv: {
+    nativeName: 'Gaelg',
+  },
+  ha: {
+    nativeName: 'هَوُسَ',
+  },
+  he: {
+    nativeName: 'עברית',
+  },
+  hi: {
+    nativeName: 'हिन्दी',
+  },
+  ho: {
+    nativeName: 'Hiri Motu',
+  },
+  hr: {
+    nativeName: 'Hrvatski',
+  },
+  ht: {
+    nativeName: 'Kreyòl ayisyen',
+  },
+  hu: {
+    nativeName: 'magyar',
+  },
+  hy: {
+    nativeName: 'Հայերեն',
+  },
+  hz: {
+    nativeName: 'Otjiherero',
+  },
+  ia: {
+    nativeName: 'Interlingua',
+  },
+  id: {
+    nativeName: 'Bahasa Indonesia',
+  },
+  ie: {
+    nativeName: 'Interlingue',
+  },
+  ig: {
+    nativeName: 'Asụsụ Igbo',
+  },
+  ii: {
+    nativeName: 'ꆈꌠ꒿ Nuosuhxop',
+  },
+  ik: {
+    nativeName: 'Iñupiaq',
+  },
+  io: {
+    nativeName: 'Ido',
+  },
+  is: {
+    nativeName: 'Íslenska',
+  },
+  it: {
+    nativeName: 'Italiano',
+  },
+  iu: {
+    nativeName: 'ᐃᓄᒃᑎᑐᑦ',
+  },
+  ja: {
+    nativeName: '日本語',
+  },
+  jv: {
+    nativeName: 'basa Jawa',
+  },
+  ka: {
+    nativeName: 'ქართული',
+  },
+  kg: {
+    nativeName: 'Kikongo',
+  },
+  ki: {
+    nativeName: 'Gĩkũyũ',
+  },
+  kj: {
+    nativeName: 'Kuanyama',
+  },
+  kk: {
+    nativeName: 'қазақ тілі',
+  },
+  kl: {
+    nativeName: 'kalaallisut',
+  },
+  km: {
+    nativeName: 'ខេមរភាសា',
+  },
+  kn: {
+    nativeName: 'ಕನ್ನಡ',
+  },
+  ko: {
+    nativeName: '한국어',
+  },
+  kr: {
+    nativeName: 'Kanuri',
+  },
+  ks: {
+    nativeName: 'कश्मीरी',
+  },
+  ku: {
+    nativeName: 'Kurmancî',
+  },
+  kv: {
+    nativeName: 'коми кыв',
+  },
+  kw: {
+    nativeName: 'Kernewek',
+  },
+  ky: {
+    nativeName: 'Кыргызча',
+  },
+  la: {
+    nativeName: 'latine',
+  },
+  lb: {
+    nativeName: 'Lëtzebuergesch',
+  },
+  lg: {
+    nativeName: 'Luganda',
+  },
+  li: {
+    nativeName: 'Limburgs',
+  },
+  ln: {
+    nativeName: 'Lingála',
+  },
+  lo: {
+    nativeName: 'ລາວ',
+  },
+  lt: {
+    nativeName: 'lietuvių kalba',
+  },
+  lu: {
+    nativeName: 'Tshiluba',
+  },
+  lv: {
+    nativeName: 'latviešu valoda',
+  },
+  mg: {
+    nativeName: 'fiteny malagasy',
+  },
+  mh: {
+    nativeName: 'Kajin M̧ajeļ',
+  },
+  mi: {
+    nativeName: 'te reo Māori',
+  },
+  mk: {
+    nativeName: 'македонски јазик',
+  },
+  ml: {
+    nativeName: 'മലയാളം',
+  },
+  mn: {
+    nativeName: 'Монгол хэл',
+  },
+  mr: {
+    nativeName: 'मराठी',
+  },
+  ms: {
+    nativeName: 'Bahasa Melayu',
+  },
+  'ms-Arab': {
+    nativeName: 'بهاس ملايو',
+  },
+  mt: {
+    nativeName: 'Malti',
+  },
+  my: {
+    nativeName: 'ဗမာစာ',
+  },
+  na: {
+    nativeName: 'Ekakairũ Naoero',
+  },
+  nb: {
+    nativeName: 'Norsk bokmål',
+  },
+  nd: {
+    nativeName: 'isiNdebele',
+  },
+  ne: {
+    nativeName: 'नेपाली',
+  },
+  ng: {
+    nativeName: 'Owambo',
+  },
+  nl: {
+    nativeName: 'Nederlands',
+  },
+  nn: {
+    nativeName: 'Norsk Nynorsk',
+  },
+  no: {
+    nativeName: 'Norsk',
+  },
+  nr: {
+    nativeName: 'isiNdebele',
+  },
+  nv: {
+    nativeName: 'Diné bizaad',
+  },
+  ny: {
+    nativeName: 'chiCheŵa',
+  },
+  oc: {
+    nativeName: 'occitan',
+  },
+  oj: {
+    nativeName: 'ᐊᓂᔑᓈᐯᒧᐎᓐ',
+  },
+  om: {
+    nativeName: 'Afaan Oromoo',
+  },
+  or: {
+    nativeName: 'ଓଡ଼ିଆ',
+  },
+  os: {
+    nativeName: 'ирон æвзаг',
+  },
+  pa: {
+    nativeName: 'ਪੰਜਾਬੀ',
+  },
+  pi: {
+    nativeName: 'पाऴि',
+  },
+  pl: {
+    nativeName: 'Polski',
+  },
+  ps: {
+    nativeName: 'پښتو',
+  },
+  pt: {
+    nativeName: 'Português',
+  },
+  qu: {
+    nativeName: 'Runa Simi',
+  },
+  rm: {
+    nativeName: 'rumantsch grischun',
+  },
+  rn: {
+    nativeName: 'Ikirundi',
+  },
+  ro: {
+    nativeName: 'Română',
+  },
+  ru: {
+    nativeName: 'Русский',
+  },
+  rw: {
+    nativeName: 'Ikinyarwanda',
+  },
+  sa: {
+    nativeName: 'संस्कृतम्',
+  },
+  sc: {
+    nativeName: 'sardu',
+  },
+  sd: {
+    nativeName: 'सिन्धी',
+  },
+  se: {
+    nativeName: 'Davvisámegiella',
+  },
+  sg: {
+    nativeName: 'yângâ tî sängö',
+  },
+  si: {
+    nativeName: 'සිංහල',
+  },
+  sk: {
+    nativeName: 'slovenčina',
+  },
+  sl: {
+    nativeName: 'slovenščina',
+  },
+  sn: {
+    nativeName: 'chiShona',
+  },
+  so: {
+    nativeName: 'Soomaaliga',
+  },
+  sq: {
+    nativeName: 'Shqip',
+  },
+  sr: {
+    nativeName: 'српски језик',
+  },
+  ss: {
+    nativeName: 'SiSwati',
+  },
+  st: {
+    nativeName: 'Sesotho',
+  },
+  su: {
+    nativeName: 'Basa Sunda',
+  },
+  sv: {
+    nativeName: 'Svenska',
+  },
+  sw: {
+    nativeName: 'Kiswahili',
+  },
+  ta: {
+    nativeName: 'தமிழ்',
+  },
+  te: {
+    nativeName: 'తెలుగు',
+  },
+  tg: {
+    nativeName: 'тоҷикӣ',
+  },
+  th: {
+    nativeName: 'ไทย',
+  },
+  ti: {
+    nativeName: 'ትግርኛ',
+  },
+  tk: {
+    nativeName: 'Türkmen',
+  },
+  tl: {
+    nativeName: 'Tagalog',
+  },
+  tn: {
+    nativeName: 'Setswana',
+  },
+  to: {
+    nativeName: 'faka Tonga',
+  },
+  tr: {
+    nativeName: 'Türkçe',
+  },
+  ts: {
+    nativeName: 'Xitsonga',
+  },
+  tt: {
+    nativeName: 'татар теле',
+  },
+  tw: {
+    nativeName: 'Twi',
+  },
+  ty: {
+    nativeName: 'Reo Tahiti',
+  },
+  ug: {
+    nativeName: 'ئۇيغۇرچە‎',
+  },
+  uk: {
+    nativeName: 'Українська',
+  },
+  ur: {
+    nativeName: 'اردو',
+  },
+  vi: {
+    nativeName: 'Tiếng Việt',
+  },
+  vo: {
+    nativeName: 'Volapük',
+  },
+  wa: {
+    nativeName: 'Walon',
+  },
+  wo: {
+    nativeName: 'Wollof',
+  },
+  xh: {
+    nativeName: 'isiXhosa',
+  },
+  yi: {
+    nativeName: 'ייִדיש',
+  },
+  zu: {
+    nativeName: 'isiZulu',
+  },
+};
+
+export const ISO_639_3 = {
+  ast: {
+    nativeName: 'Asturianu',
+  },
+  chr: {
+    nativeName: 'ᏣᎳᎩ ᎦᏬᏂᎯᏍᏗ',
+  },
+  ckb: {
+    nativeName: 'سۆرانی',
+  },
+  cnr: {
+    nativeName: 'crnogorski',
+  },
+  csb: {
+    nativeName: 'Kaszëbsczi',
+  },
+  gsw: {
+    nativeName: 'Schwiizertütsch',
+  },
+  jbo: {
+    nativeName: 'la .lojban.',
+  },
+  kab: {
+    nativeName: 'Taqbaylit',
+  },
+  ldn: {
+    nativeName: 'Láadan',
+  },
+  lfn: {
+    nativeName: 'lingua franca nova',
+  },
+  moh: {
+    nativeName: 'Kanienʼkéha',
+  },
+  nds: {
+    nativeName: 'Plattdüütsch',
+  },
+  pdc: {
+    nativeName: 'Pennsilfaani-Deitsch',
+  },
+  sco: {
+    nativeName: 'Scots',
+  },
+  sma: {
+    nativeName: 'Åarjelsaemien Gïele',
+  },
+  smj: {
+    nativeName: 'Julevsámegiella',
+  },
+  szl: {
+    nativeName: 'ślůnsko godka',
+  },
+  tok: {
+    nativeName: 'toki pona',
+  },
+  vai: {
+    nativeName: 'ꕙꔤ',
+  },
+  xal: {
+    nativeName: 'Хальмг келн',
+  },
+  zba: {
+    nativeName: 'باليبلن',
+  },
+  zgh: {
+    nativeName: 'ⵜⴰⵎⴰⵣⵉⵖⵜ',
+  },
+};
+
+export const ISO_639_1_REGIONAL = {
+  'zh-CN': {
+    nativeName: '简体中文',
+  },
+  'zh-HK': {
+    nativeName: '繁體中文（香港）',
+  },
+  'zh-TW': {
+    nativeName: '繁體中文（臺灣）',
+  },
+  'zh-YUE': {
+    nativeName: '廣東話',
+  },
+};
+
+export const SUPPORTED_POST_LOCALES = {
+	...ISO_639_1,
+  ...ISO_639_3,
+  ...ISO_639_1_REGIONAL,
+};
diff --git a/packages/frontend/src/store.ts b/packages/frontend/src/store.ts
index fbc1d0567..10c59d42e 100644
--- a/packages/frontend/src/store.ts
+++ b/packages/frontend/src/store.ts
@@ -133,6 +133,11 @@ export const defaultStore = markRaw(new Storage('base', {
 		default: [] as string[],
 	},
 
+	recentlyUsedPostLanguages: {
+		where: "account",
+		default: [] as string[],
+	},
+
 	menu: {
 		where: 'deviceAccount',
 		default: [
diff --git a/packages/misskey-js/etc/misskey-js.api.md b/packages/misskey-js/etc/misskey-js.api.md
index 94b056fa3..3b02aa17b 100644
--- a/packages/misskey-js/etc/misskey-js.api.md
+++ b/packages/misskey-js/etc/misskey-js.api.md
@@ -2391,6 +2391,9 @@ type IWebhooksShowResponse = operations['i___webhooks___show']['responses']['200
 // @public (undocumented)
 type IWebhooksUpdateRequest = operations['i___webhooks___update']['requestBody']['content']['application/json'];
 
+// @public (undocumented)
+export const languages: readonly ["ach", "ady", "af", "ak", "ar", "az", "bg", "bn", "br", "ca", "cak", "cs", "cy", "da", "de", "dsb", "el", "en", "eo", "es", "et", "eu", "fa", "ff", "fi", "fo", "fr", "ga", "gd", "gl", "gv", "he", "hi", "hr", "hsb", "ht", "hu", "hy", "id", "is", "it", "ja", "km", "kl", "kab", "kn", "ko", "kw", "la", "lb", "lt", "lv", "mai", "mk", "ml", "mr", "ms", "mt", "my", "no", "nb", "ne", "nl", "oc", "pa", "pl", "pt", "ro", "ru", "sh", "sk", "sl", "sq", "sr", "su", "sv", "sw", "ta", "te", "tg", "th", "fil", "tlh", "tr", "uk", "ur", "uz", "vi", "yi", "zh"];
+
 // @public (undocumented)
 type MeDetailed = components['schemas']['MeDetailed'];
 
diff --git a/packages/misskey-js/src/autogen/types.ts b/packages/misskey-js/src/autogen/types.ts
index 7b6bcca1a..24c39a56c 100644
--- a/packages/misskey-js/src/autogen/types.ts
+++ b/packages/misskey-js/src/autogen/types.ts
@@ -4244,6 +4244,8 @@ export type components = {
       /** Format: date-time */
       deletedAt?: string | null;
       text: string | null;
+      /** @enum {string|null} */
+      lang: 'ach' | 'ady' | 'af' | 'af-NA' | 'af-ZA' | 'ak' | 'ar' | 'ar-AR' | 'ar-MA' | 'ar-SA' | 'ay-BO' | 'az' | 'az-AZ' | 'be-BY' | 'bg' | 'bg-BG' | 'bn' | 'bn-IN' | 'bn-BD' | 'br' | 'bs-BA' | 'ca' | 'ca-ES' | 'cak' | 'ck-US' | 'cs' | 'cs-CZ' | 'cy' | 'cy-GB' | 'da' | 'da-DK' | 'de' | 'de-AT' | 'de-DE' | 'de-CH' | 'dsb' | 'el' | 'el-GR' | 'en' | 'en-GB' | 'en-AU' | 'en-CA' | 'en-IE' | 'en-IN' | 'en-PI' | 'en-SG' | 'en-UD' | 'en-US' | 'en-ZA' | 'en@pirate' | 'eo' | 'eo-EO' | 'es' | 'es-AR' | 'es-419' | 'es-CL' | 'es-CO' | 'es-EC' | 'es-ES' | 'es-LA' | 'es-NI' | 'es-MX' | 'es-US' | 'es-VE' | 'et' | 'et-EE' | 'eu' | 'eu-ES' | 'fa' | 'fa-IR' | 'fb-LT' | 'ff' | 'fi' | 'fi-FI' | 'fo' | 'fo-FO' | 'fr' | 'fr-CA' | 'fr-FR' | 'fr-BE' | 'fr-CH' | 'fy-NL' | 'ga' | 'ga-IE' | 'gd' | 'gl' | 'gl-ES' | 'gn-PY' | 'gu-IN' | 'gv' | 'gx-GR' | 'he' | 'he-IL' | 'hi' | 'hi-IN' | 'hr' | 'hr-HR' | 'hsb' | 'ht' | 'hu' | 'hu-HU' | 'hy' | 'hy-AM' | 'id' | 'id-ID' | 'is' | 'is-IS' | 'it' | 'it-IT' | 'ja' | 'ja-JP' | 'jv-ID' | 'ka-GE' | 'kk-KZ' | 'km' | 'kl' | 'km-KH' | 'kab' | 'kn' | 'kn-IN' | 'ko' | 'ko-KR' | 'ku-TR' | 'kw' | 'la' | 'la-VA' | 'lb' | 'li-NL' | 'lt' | 'lt-LT' | 'lv' | 'lv-LV' | 'mai' | 'mg-MG' | 'mk' | 'mk-MK' | 'ml' | 'ml-IN' | 'mn-MN' | 'mr' | 'mr-IN' | 'ms' | 'ms-MY' | 'mt' | 'mt-MT' | 'my' | 'no' | 'nb' | 'nb-NO' | 'ne' | 'ne-NP' | 'nl' | 'nl-BE' | 'nl-NL' | 'nn-NO' | 'oc' | 'or-IN' | 'pa' | 'pa-IN' | 'pl' | 'pl-PL' | 'ps-AF' | 'pt' | 'pt-BR' | 'pt-PT' | 'qu-PE' | 'rm-CH' | 'ro' | 'ro-RO' | 'ru' | 'ru-RU' | 'sa-IN' | 'se-NO' | 'sh' | 'si-LK' | 'sk' | 'sk-SK' | 'sl' | 'sl-SI' | 'so-SO' | 'sq' | 'sq-AL' | 'sr' | 'sr-RS' | 'su' | 'sv' | 'sv-SE' | 'sw' | 'sw-KE' | 'ta' | 'ta-IN' | 'te' | 'te-IN' | 'tg' | 'tg-TJ' | 'th' | 'th-TH' | 'fil' | 'tlh' | 'tr' | 'tr-TR' | 'tt-RU' | 'uk' | 'uk-UA' | 'ur' | 'ur-PK' | 'uz' | 'uz-UZ' | 'vi' | 'vi-VN' | 'xh-ZA' | 'yi' | 'yi-DE' | 'zh' | 'zh-Hans' | 'zh-Hant' | 'zh-CN' | 'zh-HK' | 'zh-SG' | 'zh-TW' | 'zu-ZA';
       cw?: string | null;
       /** Format: id */
       userId: string;
@@ -23564,6 +23566,8 @@ export type operations = {
           /** Format: misskey:id */
           channelId?: string | null;
           text?: string | null;
+          /** @enum {string|null} */
+          lang?: 'ach' | 'ady' | 'af' | 'af-NA' | 'af-ZA' | 'ak' | 'ar' | 'ar-AR' | 'ar-MA' | 'ar-SA' | 'ay-BO' | 'az' | 'az-AZ' | 'be-BY' | 'bg' | 'bg-BG' | 'bn' | 'bn-IN' | 'bn-BD' | 'br' | 'bs-BA' | 'ca' | 'ca-ES' | 'cak' | 'ck-US' | 'cs' | 'cs-CZ' | 'cy' | 'cy-GB' | 'da' | 'da-DK' | 'de' | 'de-AT' | 'de-DE' | 'de-CH' | 'dsb' | 'el' | 'el-GR' | 'en' | 'en-GB' | 'en-AU' | 'en-CA' | 'en-IE' | 'en-IN' | 'en-PI' | 'en-SG' | 'en-UD' | 'en-US' | 'en-ZA' | 'en@pirate' | 'eo' | 'eo-EO' | 'es' | 'es-AR' | 'es-419' | 'es-CL' | 'es-CO' | 'es-EC' | 'es-ES' | 'es-LA' | 'es-NI' | 'es-MX' | 'es-US' | 'es-VE' | 'et' | 'et-EE' | 'eu' | 'eu-ES' | 'fa' | 'fa-IR' | 'fb-LT' | 'ff' | 'fi' | 'fi-FI' | 'fo' | 'fo-FO' | 'fr' | 'fr-CA' | 'fr-FR' | 'fr-BE' | 'fr-CH' | 'fy-NL' | 'ga' | 'ga-IE' | 'gd' | 'gl' | 'gl-ES' | 'gn-PY' | 'gu-IN' | 'gv' | 'gx-GR' | 'he' | 'he-IL' | 'hi' | 'hi-IN' | 'hr' | 'hr-HR' | 'hsb' | 'ht' | 'hu' | 'hu-HU' | 'hy' | 'hy-AM' | 'id' | 'id-ID' | 'is' | 'is-IS' | 'it' | 'it-IT' | 'ja' | 'ja-JP' | 'jv-ID' | 'ka-GE' | 'kk-KZ' | 'km' | 'kl' | 'km-KH' | 'kab' | 'kn' | 'kn-IN' | 'ko' | 'ko-KR' | 'ku-TR' | 'kw' | 'la' | 'la-VA' | 'lb' | 'li-NL' | 'lt' | 'lt-LT' | 'lv' | 'lv-LV' | 'mai' | 'mg-MG' | 'mk' | 'mk-MK' | 'ml' | 'ml-IN' | 'mn-MN' | 'mr' | 'mr-IN' | 'ms' | 'ms-MY' | 'mt' | 'mt-MT' | 'my' | 'no' | 'nb' | 'nb-NO' | 'ne' | 'ne-NP' | 'nl' | 'nl-BE' | 'nl-NL' | 'nn-NO' | 'oc' | 'or-IN' | 'pa' | 'pa-IN' | 'pl' | 'pl-PL' | 'ps-AF' | 'pt' | 'pt-BR' | 'pt-PT' | 'qu-PE' | 'rm-CH' | 'ro' | 'ro-RO' | 'ru' | 'ru-RU' | 'sa-IN' | 'se-NO' | 'sh' | 'si-LK' | 'sk' | 'sk-SK' | 'sl' | 'sl-SI' | 'so-SO' | 'sq' | 'sq-AL' | 'sr' | 'sr-RS' | 'su' | 'sv' | 'sv-SE' | 'sw' | 'sw-KE' | 'ta' | 'ta-IN' | 'te' | 'te-IN' | 'tg' | 'tg-TJ' | 'th' | 'th-TH' | 'fil' | 'tlh' | 'tr' | 'tr-TR' | 'tt-RU' | 'uk' | 'uk-UA' | 'ur' | 'ur-PK' | 'uz' | 'uz-UZ' | 'vi' | 'vi-VN' | 'xh-ZA' | 'yi' | 'yi-DE' | 'zh' | 'zh-Hans' | 'zh-Hant' | 'zh-CN' | 'zh-HK' | 'zh-SG' | 'zh-TW' | 'zu-ZA';
           fileIds?: string[];
           mediaIds?: string[];
           poll?: ({
diff --git a/packages/misskey-js/src/consts.ts b/packages/misskey-js/src/consts.ts
index 470490c15..d660a891e 100644
--- a/packages/misskey-js/src/consts.ts
+++ b/packages/misskey-js/src/consts.ts
@@ -398,3 +398,97 @@ export type ModerationLogPayloads = {
 		mutualLinkSections: string;
 	};
 };
+
+
+export const languages = [
+	"ach",
+	"ady",
+	"af",
+	"ak",
+	"ar",
+	"az",
+	"bg",
+	"bn",
+	"br",
+	"ca",
+	"cak",
+	"cs",
+	"cy",
+	"da",
+	"de",
+	"dsb",
+	"el",
+	"en",
+	"eo",
+	"es",
+	"et",
+	"eu",
+	"fa",
+	"ff",
+	"fi",
+	"fo",
+	"fr",
+	"ga",
+	"gd",
+	"gl",
+	"gv",
+	"he",
+	"hi",
+	"hr",
+	"hsb",
+	"ht",
+	"hu",
+	"hy",
+	"id",
+	"is",
+	"it",
+	"ja",
+	"km",
+	"kl",
+	"kab",
+	"kn",
+	"ko",
+	"kw",
+	"la",
+	"lb",
+	"lt",
+	"lv",
+	"mai",
+	"mk",
+	"ml",
+	"mr",
+	"ms",
+	"mt",
+	"my",
+	"no",
+	"nb",
+	"ne",
+	"nl",
+	"oc",
+	"pa",
+	"pl",
+	"pt",
+	"ro",
+	"ru",
+	"sh",
+	"sk",
+	"sl",
+	"sq",
+	"sr",
+	"su",
+	"sv",
+	"sw",
+	"ta",
+	"te",
+	"tg",
+	"th",
+	"fil",
+	"tlh",
+	"tr",
+	"uk",
+	"ur",
+	"uz",
+	"vi",
+	"yi",
+	"zh",
+] as const;
diff --git a/packages/misskey-js/src/index.ts b/packages/misskey-js/src/index.ts
index 54cae8ec0..0594c297f 100644
--- a/packages/misskey-js/src/index.ts
+++ b/packages/misskey-js/src/index.ts
@@ -15,6 +15,7 @@ export {
 export const permissions = consts.permissions;
 export const notificationTypes = consts.notificationTypes;
 export const noteVisibilities = consts.noteVisibilities;
+export const languages = consts.languages;
 export const mutedNoteReasons = consts.mutedNoteReasons;
 export const followingVisibilities = consts.followingVisibilities;
 export const followersVisibilities = consts.followersVisibilities;