diff --git a/adapter/src/utils/useLocale.js b/adapter/src/utils/useLocale.js
index ce7cc09d..e0672d48 100644
--- a/adapter/src/utils/useLocale.js
+++ b/adapter/src/utils/useLocale.js
@@ -27,6 +27,7 @@ export const useLocale = ({ userSettings, configDirection }) => {
         // Intl.Locale dir utils aren't supported in firefox, so use i18n
         const localeDirection = i18n.dir(locale.language)
         setDocumentDirection({ localeDirection, configDirection })
+        document.documentElement.setAttribute('lang', locale.baseName)
 
         setResult({ locale, direction: localeDirection })
     }, [userSettings, configDirection])
diff --git a/adapter/src/utils/useLocale.test.js b/adapter/src/utils/useLocale.test.js
index de387b98..00be9ca0 100644
--- a/adapter/src/utils/useLocale.test.js
+++ b/adapter/src/utils/useLocale.test.js
@@ -301,3 +301,20 @@ describe('config direction is respected for the document direction', () => {
         )
     })
 })
+
+test('document `lang` attribute is set', () => {
+    jest.spyOn(document.documentElement, 'setAttribute')
+    const userSettings = { keyUiLocale: 'pt-BR' }
+
+    renderHook(() =>
+        useLocale({
+            userSettings,
+            configDirection: undefined,
+        })
+    )
+
+    expect(document.documentElement.setAttribute).toHaveBeenCalledWith(
+        'lang',
+        'pt-BR'
+    )
+})