diff --git a/locales/en-US.yml b/locales/en-US.yml
index f4ff6fac91..804b9281b4 100644
--- a/locales/en-US.yml
+++ b/locales/en-US.yml
@@ -1139,6 +1139,8 @@ confirm: "Confirm"
 importZip: "Import ZIP"
 exportZip: "Export ZIP"
 emojiPackCreator: "Emoji pack creator"
+languageForTranslation: "Post translation language"
+detectPostLanguage: "Automatically detect the language and show a translate button for posts in foreign languages"
 
 _sensitiveMediaDetection:
   description: "Reduces the effort of server moderation through automatically recognizing
diff --git a/locales/ja-JP.yml b/locales/ja-JP.yml
index 76b7aa434b..d7884eccdd 100644
--- a/locales/ja-JP.yml
+++ b/locales/ja-JP.yml
@@ -988,6 +988,8 @@ youHaveUnreadAnnouncements: "未読のお知らせがあります"
 neverShow: "今後表示しない"
 remindMeLater: "また後で"
 addRe: "閲覧注意の投稿への返信で、注釈の先頭に\"re:\"を追加する"
+languageForTranslation: "投稿翻訳に使用する言語" 
+detectPostLanguage: "投稿の言語を自動検出し、外国語の投稿に翻訳ボタンを表示する" 
 
 _sensitiveMediaDetection:
   description: "機械学習を使って自動でセンシティブなメディアを検出し、モデレーションに役立てられます。サーバーの負荷が少し増えます。"
diff --git a/packages/client/package.json b/packages/client/package.json
index d371254bf8..6bd13bac95 100644
--- a/packages/client/package.json
+++ b/packages/client/package.json
@@ -81,6 +81,7 @@
 		"three": "0.156.0",
 		"throttle-debounce": "5.0.0",
 		"tinycolor2": "1.6.0",
+		"tinyld": "^1.3.4",
 		"tsc-alias": "1.8.7",
 		"tsconfig-paths": "4.2.0",
 		"twemoji-parser": "14.0.0",
diff --git a/packages/client/src/components/MkNote.vue b/packages/client/src/components/MkNote.vue
index 539b734d69..bfd2b6e68d 100644
--- a/packages/client/src/components/MkNote.vue
+++ b/packages/client/src/components/MkNote.vue
@@ -219,6 +219,14 @@
 						<i class="ph-minus ph-bold ph-lg"></i>
 					</button>
 					<XQuoteButton class="button" :note="appearNote" />
+					<button
+						v-if="isForeignLanguage && translation == null"
+						class="button _button"
+						@click.stop="translate"
+						v-tooltip.noDelay.bottom="i18n.ts.translate"
+					>
+						<i class="ph-translate ph-bold ph-lg"></i>
+					</button>
 					<button
 						ref="menuButton"
 						v-tooltip.noDelay.bottom="i18n.ts.more"
@@ -259,6 +267,7 @@ import { computed, inject, onMounted, ref } from "vue";
 import * as mfm from "mfm-js";
 import type { Ref } from "vue";
 import type * as misskey from "firefish-js";
+import { detect as detectLanguage_ } from "tinyld";
 import MkSubNoteContent from "./MkSubNoteContent.vue";
 import MkNoteSub from "@/components/MkNoteSub.vue";
 import XNoteHeader from "@/components/MkNoteHeader.vue";
@@ -346,6 +355,57 @@ const translation = ref(null);
 const translating = ref(false);
 const enableEmojiReactions = defaultStore.state.enableEmojiReactions;
 const expandOnNoteClick = defaultStore.state.expandOnNoteClick;
+const lang = localStorage.getItem("lang");
+const translateLang = localStorage.getItem("translateLang");
+
+function detectLanguage(text: string) {
+	const nodes = mfm.parse(text);
+	const filtered = mfm.extract(nodes, (node) => {
+		return node.type === "text" || node.type === "quote";
+	});
+	const purified = mfm.toString(filtered);
+	return detectLanguage_(purified);
+}
+
+const isForeignLanguage: boolean =
+	defaultStore.state.detectPostLanguage &&
+	appearNote.value.text != null &&
+	(() => {
+		const targetLang = (translateLang || lang || navigator.language)?.slice(
+			0,
+			2,
+		);
+		const postLang = detectLanguage(appearNote.value.text);
+		return postLang !== "" && postLang !== targetLang;
+	})();
+
+async function translate_(noteId: number, targetLang: string) {
+	return await os.api("notes/translate", {
+		noteId: noteId,
+		targetLang: targetLang,
+	});
+}
+
+async function translate() {
+	if (translation.value != null) return;
+	translating.value = true;
+	translation.value = await translate_(
+		appearNote.value.id,
+		translateLang || lang || navigator.language,
+	);
+
+	// use UI language as the second translation language
+	if (
+		translateLang != null &&
+		lang != null &&
+		translateLang !== lang &&
+		(!translation.value ||
+			translation.value.sourceLang.toLowerCase() ===
+				translateLang.slice(0, 2))
+	)
+		translation.value = await translate_(appearNote.value.id, lang);
+	translating.value = false;
+}
 
 const keymap = {
 	r: () => reply(true),
diff --git a/packages/client/src/components/MkNoteSub.vue b/packages/client/src/components/MkNoteSub.vue
index 11db10dddf..e27e838470 100644
--- a/packages/client/src/components/MkNoteSub.vue
+++ b/packages/client/src/components/MkNoteSub.vue
@@ -124,6 +124,14 @@
 						<i class="ph-minus ph-bold ph-lg"></i>
 					</button>
 					<XQuoteButton class="button" :note="appearNote" />
+					<button
+						v-if="isForeignLanguage && translation == null"
+						class="button _button"
+						@click.stop="translate"
+						v-tooltip.noDelay.bottom="i18n.ts.translate"
+					>
+						<i class="ph-translate ph-bold ph-lg"></i>
+					</button>
 					<button
 						ref="menuButton"
 						v-tooltip.noDelay.bottom="i18n.ts.more"
@@ -180,6 +188,8 @@
 import { computed, inject, ref } from "vue";
 import type { Ref } from "vue";
 import type * as misskey from "firefish-js";
+import type * as mfm from "mfm-js";
+import { detect as detectLanguage_ } from "tinyld";
 import XNoteHeader from "@/components/MkNoteHeader.vue";
 import MkSubNoteContent from "@/components/MkSubNoteContent.vue";
 import XReactionsViewer from "@/components/MkReactionsViewer.vue";
@@ -266,6 +276,57 @@ const replies: misskey.entities.Note[] =
 		.reverse() ?? [];
 const enableEmojiReactions = defaultStore.state.enableEmojiReactions;
 const expandOnNoteClick = defaultStore.state.expandOnNoteClick;
+const lang = localStorage.getItem("lang");
+const translateLang = localStorage.getItem("translateLang");
+
+function detectLanguage(text: string) {
+	const nodes = mfm.parse(text);
+	const filtered = mfm.extract(nodes, (node) => {
+		return node.type === "text" || node.type === "quote";
+	});
+	const purified = mfm.toString(filtered);
+	return detectLanguage_(purified);
+}
+
+const isForeignLanguage: boolean =
+	defaultStore.state.detectPostLanguage &&
+	appearNote.value.text != null &&
+	(() => {
+		const targetLang = (translateLang || lang || navigator.language)?.slice(
+			0,
+			2,
+		);
+		const postLang = detectLanguage(appearNote.value.text);
+		return postLang !== "" && postLang !== targetLang;
+	})();
+
+async function translate_(noteId: number, targetLang: string) {
+	return await os.api("notes/translate", {
+		noteId: noteId,
+		targetLang: targetLang,
+	});
+}
+
+async function translate() {
+	if (translation.value != null) return;
+	translating.value = true;
+	translation.value = await translate_(
+		appearNote.value.id,
+		translateLang || lang || navigator.language,
+	);
+
+	// use UI language as the second translation language
+	if (
+		translateLang != null &&
+		lang != null &&
+		translateLang !== lang &&
+		(!translation.value ||
+			translation.value.sourceLang.toLowerCase() ===
+				translateLang.slice(0, 2))
+	)
+		translation.value = await translate_(appearNote.value.id, lang);
+	translating.value = false;
+}
 
 useNoteCapture({
 	rootEl: el,
diff --git a/packages/client/src/pages/settings/general.vue b/packages/client/src/pages/settings/general.vue
index 93cc6b2de6..931b771bcd 100644
--- a/packages/client/src/pages/settings/general.vue
+++ b/packages/client/src/pages/settings/general.vue
@@ -17,6 +17,15 @@
 			</template>
 		</FormSelect>
 
+		<FormSelect v-model="translateLang" class="_formBlock">
+			<template #label>
+				{{ i18n.ts.languageForTranslation }}
+			</template>
+			<option v-for="x in langs" :key="x[0]" :value="x[0]">
+				{{ x[1] }}
+			</option>
+		</FormSelect>
+
 		<FormRadios v-model="overridedDeviceKind" class="_formBlock">
 			<template #label>{{ i18n.ts.overridedDeviceKind }}</template>
 			<option :value="null">{{ i18n.ts.auto }}</option>
@@ -71,6 +80,9 @@
 					{{ i18n.ts.reflectMayTakeTime }}</template
 				></FormSwitch
 			>
+			<FormSwitch v-model="detectPostLanguage" class="_formBlock">{{
+				i18n.ts.detectPostLanguage
+			}}</FormSwitch>
 
 			<FormSelect v-model="serverDisconnectedBehavior" class="_formBlock">
 				<template #label>{{ i18n.ts.whenServerDisconnected }}</template>
@@ -266,6 +278,7 @@ import { definePageMetadata } from "@/scripts/page-metadata";
 import { deviceKind } from "@/scripts/device-kind";
 
 const lang = ref(localStorage.getItem("lang"));
+const translateLang = ref(localStorage.getItem("translateLang"));
 const fontSize = ref(localStorage.getItem("fontSize"));
 const useSystemFont = ref(localStorage.getItem("useSystemFont") != null);
 
@@ -357,6 +370,9 @@ const showAdminUpdates = computed(
 const showTimelineReplies = computed(
 	defaultStore.makeGetterSetter("showTimelineReplies"),
 );
+const detectPostLanguage = computed(
+	defaultStore.makeGetterSetter("detectPostLanguage"),
+);
 
 watch(swipeOnDesktop, () => {
 	defaultStore.set("swipeOnMobile", true);
@@ -367,6 +383,10 @@ watch(lang, () => {
 	localStorage.removeItem("locale");
 });
 
+watch(translateLang, () => {
+	localStorage.setItem("translateLang", translateLang.value as string);
+});
+
 watch(fontSize, () => {
 	if (fontSize.value == null) {
 		localStorage.removeItem("fontSize");
@@ -386,6 +406,7 @@ watch(useSystemFont, () => {
 watch(
 	[
 		lang,
+		translateLang,
 		fontSize,
 		useSystemFont,
 		enableInfiniteScroll,
diff --git a/packages/client/src/scripts/get-note-menu.ts b/packages/client/src/scripts/get-note-menu.ts
index 31361db962..38fc6c8f37 100644
--- a/packages/client/src/scripts/get-note-menu.ts
+++ b/packages/client/src/scripts/get-note-menu.ts
@@ -237,15 +237,35 @@ export function getNoteMenu(props: {
 		});
 	}
 
+	async function translate_(noteId: number, targetLang: string) {
+		return await os.api("notes/translate", {
+			noteId: noteId,
+			targetLang: targetLang,
+		});
+	}
+
 	async function translate(): Promise<void> {
+		const translateLang = localStorage.getItem("translateLang");
+		const lang = localStorage.getItem("lang");
+
 		if (props.translation.value != null) return;
 		props.translating.value = true;
-		const res = await os.api("notes/translate", {
-			noteId: appearNote.id,
-			targetLang: localStorage.getItem("lang") || navigator.language,
-		});
+		props.translation.value = await translate_(
+			appearNote.id,
+			translateLang || lang || navigator.language,
+		);
+
+		// use UI language as the second translation target
+		if (
+			translateLang != null &&
+			lang != null &&
+			translateLang !== lang &&
+			(!props.translation.value ||
+				props.translation.value.sourceLang.toLowerCase() ===
+					translateLang.slice(0, 2))
+		)
+			props.translation.value = await translate_(appearNote.id, lang);
 		props.translating.value = false;
-		props.translation.value = res;
 	}
 
 	let menu;
diff --git a/packages/client/src/store.ts b/packages/client/src/store.ts
index 106c7a8d3e..e1f8a84067 100644
--- a/packages/client/src/store.ts
+++ b/packages/client/src/store.ts
@@ -1,6 +1,5 @@
 import { markRaw, ref } from "vue";
 import { Storage } from "./pizzax";
-import { Theme } from "./scripts/theme";
 
 export const postFormActions = [];
 export const userActions = [];
@@ -346,6 +345,10 @@ export const defaultStore = markRaw(
 			where: "account",
 			default: true,
 		},
+		detectPostLanguage: {
+			where: "deviceAccount",
+			default: true,
+		},
 	}),
 );
 
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 4813e6de64..332c285a09 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -830,6 +830,9 @@ importers:
       tinycolor2:
         specifier: 1.6.0
         version: 1.6.0
+      tinyld:
+        specifier: ^1.3.4
+        version: 1.3.4
       tsc-alias:
         specifier: 1.8.7
         version: 1.8.7
@@ -18042,6 +18045,12 @@ packages:
   /tinycolor2@1.6.0:
     resolution: {integrity: sha512-XPaBkWQJdsf3pLKJV9p4qN/S+fm2Oj8AIPo1BTUhg5oxkvm9+SVEGFdhyOz7tTdUTfvxMiAs4sp6/eZO2Ew+pw==}
 
+  /tinyld@1.3.4:
+    resolution: {integrity: sha512-u26CNoaInA4XpDU+8s/6Cq8xHc2T5M4fXB3ICfXPokUQoLzmPgSZU02TAkFwFMJCWTjk53gtkS8pETTreZwCqw==}
+    engines: {node: '>= 12.10.0', npm: '>= 6.12.0', yarn: '>= 1.20.0'}
+    hasBin: true
+    dev: true
+
   /titleize@3.0.0:
     resolution: {integrity: sha512-KxVu8EYHDPBdUYdKZdKtU2aj2XfEx9AfjXxE/Aj0vT06w2icA09Vus1rh6eSu1y01akYg6BjIK/hxyLJINoMLQ==}
     engines: {node: '>=12'}