diff --git a/app/layout.tsx b/app/layout.tsx
index f3b78ea..80d4e48 100644
--- a/app/layout.tsx
+++ b/app/layout.tsx
@@ -14,7 +14,7 @@ export const metadata: Metadata = {
 export default function RootLayout({ children }: { children: React.ReactNode }) {
   return (
     <html lang="en">
-      <body className={`${fraunces.variable} ${publicSans.variable}`}>
+      <body className={`${fraunces.variable} ${publicSans.variable} flex flex-col min-h-screen`}>
         {children}
         <Footer />
       </body>
diff --git a/app/not-found.tsx b/app/not-found.tsx
new file mode 100644
index 0000000..8763573
--- /dev/null
+++ b/app/not-found.tsx
@@ -0,0 +1,13 @@
+import { Link } from '$shared/ui';
+
+/**
+ * Custom 404 page — shown for any unmatched route.
+ */
+export default function NotFound() {
+  return (
+    <main className="flex-1 flex flex-col items-center justify-center gap-6">
+      <h1 className="font-heading text-[clamp(8rem,20vw,18rem)] leading-none">404</h1>
+      <Link href="/">Back to main</Link>
+    </main>
+  );
+}
