diff --git a/src/frontend/apps/impress/src/features/language/components/LanguagePicker.tsx b/src/frontend/apps/impress/src/features/language/components/LanguagePicker.tsx
index a9b60836e..47bc98937 100644
--- a/src/frontend/apps/impress/src/features/language/components/LanguagePicker.tsx
+++ b/src/frontend/apps/impress/src/features/language/components/LanguagePicker.tsx
@@ -10,10 +10,7 @@ import { css } from 'styled-components';
 import { Box, DropdownMenu, Icon } from '@/components/';
 import { useConfig } from '@/core';
 import { useAuthQuery } from '@/features/auth';
-import {
-  getMatchingLocales,
-  useSynchronizedLanguage,
-} from '@/features/language';
+import { getClosestLocale, useSynchronizedLanguage } from '@/features/language';
 import { useResponsiveStore } from '@/stores/useResponsiveStore';
 
 /**
@@ -35,12 +32,16 @@ export const LanguagePickerLegacy = () => {
   // Compute options for dropdown
   const optionsPicker = useMemo(() => {
     const backendOptions = conf?.LANGUAGES ?? [[language, language]];
+    const currentLocale = getClosestLocale(
+      backendOptions.map(([locale]) => locale),
+      language,
+    );
     return backendOptions.map(([backendLocale, backendLabel]) => {
       return {
         label: backendLabel,
         lang: toLangTag(backendLocale),
         value: backendLocale,
-        isSelected: getMatchingLocales([backendLocale], [language]).length > 0,
+        isSelected: backendLocale === currentLocale,
         callback: async () => {
           await changeLanguageSynchronized(backendLocale, user);
           announce(
@@ -56,8 +57,12 @@ export const LanguagePickerLegacy = () => {
   }, [changeLanguageSynchronized, conf?.LANGUAGES, language, t, user]);
 
   // Extract current language label for display
+  const currentLocale = getClosestLocale(
+    conf?.LANGUAGES.map(([code]) => code) ?? [],
+    language,
+  );
   const [currentLanguageCode, currentLanguageLabel] = conf?.LANGUAGES.find(
-    ([code]) => getMatchingLocales([code], [language]).length > 0,
+    ([code]) => code === currentLocale,
   ) ?? [language, language];
 
   return (
@@ -109,10 +114,14 @@ export const LanguagePicker = () => {
 
   const languages: LanguagesOption[] = useMemo(() => {
     const backendOptions = conf?.LANGUAGES ?? [[language, language]];
+    const currentLocale = getClosestLocale(
+      backendOptions.map(([locale]) => locale),
+      language,
+    );
     return backendOptions.map(([backendLocale, backendLabel]) => ({
       label: backendLabel,
       value: backendLocale,
-      isChecked: getMatchingLocales([backendLocale], [language]).length > 0,
+      isChecked: backendLocale === currentLocale,
     }));
   }, [conf?.LANGUAGES, language]);
 
diff --git a/src/frontend/apps/impress/src/features/language/utils/__tests__/locale.test.ts b/src/frontend/apps/impress/src/features/language/utils/__tests__/locale.test.ts
new file mode 100644
index 000000000..4528b12e1
--- /dev/null
+++ b/src/frontend/apps/impress/src/features/language/utils/__tests__/locale.test.ts
@@ -0,0 +1,44 @@
+import { describe, expect, it } from 'vitest';
+
+import { getClosestLocale, getMatchingLocales } from '../locale';
+
+const LOCALES = ['en-us', 'fr-fr', 'zh-cn', 'zh-tw'];
+
+describe('getMatchingLocales', () => {
+  it('returns every region of a language on a soft match', () => {
+    expect(getMatchingLocales(LOCALES, ['zh'])).toEqual(['zh-cn', 'zh-tw']);
+  });
+
+  it('only returns the exact match when there is one', () => {
+    expect(getMatchingLocales(LOCALES, ['zh-TW'])).toEqual(['zh-tw']);
+  });
+});
+
+describe('getClosestLocale', () => {
+  it.each([
+    ['zh-tw', 'zh-tw'],
+    ['zh-cn', 'zh-cn'],
+    ['zh-TW', 'zh-tw'],
+    ['fr', 'fr-fr'],
+    ['fr-CA', 'fr-fr'],
+    ['en', 'en-us'],
+  ])('resolves %s to %s', (language, expected) => {
+    expect(getClosestLocale(LOCALES, language)).toBe(expected);
+  });
+
+  it('prefers the exact match over the first region of the language', () => {
+    expect(getClosestLocale(['en-us', 'en-gb'], 'en-gb')).toBe('en-gb');
+  });
+
+  it('returns a single locale, never every region', () => {
+    const selected = LOCALES.filter(
+      (locale) => locale === getClosestLocale(LOCALES, 'zh-tw'),
+    );
+    expect(selected).toEqual(['zh-tw']);
+  });
+
+  it('returns undefined when no locale shares the language', () => {
+    expect(getClosestLocale(LOCALES, 'ja')).toBeUndefined();
+    expect(getClosestLocale([], 'fr')).toBeUndefined();
+  });
+});
diff --git a/src/frontend/apps/impress/src/features/language/utils/locale.ts b/src/frontend/apps/impress/src/features/language/utils/locale.ts
index 19868b944..666619b8a 100644
--- a/src/frontend/apps/impress/src/features/language/utils/locale.ts
+++ b/src/frontend/apps/impress/src/features/language/utils/locale.ts
@@ -47,3 +47,19 @@ export function getMatchingLocales(
   }
   return matchingLocales;
 }
+
+/**
+ * Finds the single available locale closest to the given one. Unlike
+ * getMatchingLocales, which returns every region of a language on a soft
+ * match, this is what to use to mark one entry as selected.
+ *
+ * @param {readonly string[]} localesAvailable - The list of available locale strings.
+ * @param {string} locale - The locale to search for.
+ * @returns {string | undefined} The exact match, else the first locale sharing the language.
+ */
+export function getClosestLocale(
+  localesAvailable: readonly string[],
+  locale: string,
+): string | undefined {
+  return getMatchingLocales(localesAvailable, [locale])[0];
+}