diff --git a/superset-frontend/src/views/App.tsx b/superset-frontend/src/views/App.tsx
index 270a344d817..4f30a552e94 100644
--- a/superset-frontend/src/views/App.tsx
+++ b/superset-frontend/src/views/App.tsx
@@ -49,6 +49,14 @@ setupAGGridModules();
 
 const bootstrapData = getBootstrapData();
 
+// WCAG 3.1.2: Set the HTML lang attribute based on the current locale
+// so screen readers announce the correct language for the page content.
+// Normalize to BCP-47 format by replacing underscores with hyphens
+// so region subtags like "pt_BR" become valid "pt-BR" rather than being dropped.
+const locale =
+  bootstrapData.common?.locale || window.navigator.language || 'en';
+document.documentElement.lang = String(locale).replace(/_/g, '-');
+
 let lastLocationPathname: string;
 
 const boundActions = bindActionCreators({ logEvent }, store.dispatch);