diff --git a/frontend/app/components/IntlProvider.tsx b/frontend/app/components/IntlProvider.tsx
index 912a9da..aea34e5 100644
--- a/frontend/app/components/IntlProvider.tsx
+++ b/frontend/app/components/IntlProvider.tsx
@@ -14,11 +14,14 @@ import caNavigation from "../../locales/ca/navigation.json";
 import esExchange from "../../locales/es/exchange.json";
 import enExchange from "../../locales/en/exchange.json";
 import caExchange from "../../locales/ca/exchange.json";
+import esAuth from "../../locales/es/auth.json";
+import enAuth from "../../locales/en/auth.json";
+import caAuth from "../../locales/ca/auth.json";
 
 const messages = {
-  es: { common: esCommon, navigation: esNavigation, exchange: esExchange },
-  en: { common: enCommon, navigation: enNavigation, exchange: enExchange },
-  ca: { common: caCommon, navigation: caNavigation, exchange: caExchange },
+  es: { common: esCommon, navigation: esNavigation, exchange: esExchange, auth: esAuth },
+  en: { common: enCommon, navigation: enNavigation, exchange: enExchange, auth: enAuth },
+  ca: { common: caCommon, navigation: caNavigation, exchange: caExchange, auth: caAuth },
 };
 
 interface IntlProviderProps {
diff --git a/frontend/app/login/page.test.tsx b/frontend/app/login/page.test.tsx
index 9d1c9ba..2d51738 100644
--- a/frontend/app/login/page.test.tsx
+++ b/frontend/app/login/page.test.tsx
@@ -19,21 +19,21 @@ afterEach(() => cleanup());
 
 test("renders login form with title", () => {
   renderWithProviders(<LoginPage />);
-  expect(screen.getByText("Welcome back")).toBeDefined();
+  expect(screen.getByText("Bienvenido de nuevo")).toBeDefined();
 });
 
 test("renders email and password inputs", () => {
   renderWithProviders(<LoginPage />);
-  expect(screen.getByLabelText("Email")).toBeDefined();
-  expect(screen.getByLabelText("Password")).toBeDefined();
+  expect(screen.getByLabelText("Correo electrónico")).toBeDefined();
+  expect(screen.getByLabelText("Contraseña")).toBeDefined();
 });
 
 test("renders sign in button", () => {
   renderWithProviders(<LoginPage />);
-  expect(screen.getByRole("button", { name: "Sign in" })).toBeDefined();
+  expect(screen.getByRole("button", { name: "Iniciar sesión" })).toBeDefined();
 });
 
 test("renders link to signup", () => {
   renderWithProviders(<LoginPage />);
-  expect(screen.getByText("Sign up")).toBeDefined();
+  expect(screen.getByText("Regístrate")).toBeDefined();
 });
diff --git a/frontend/app/login/page.tsx b/frontend/app/login/page.tsx
index bb8d0ba..19a3d06 100644
--- a/frontend/app/login/page.tsx
+++ b/frontend/app/login/page.tsx
@@ -5,6 +5,7 @@ import { useRouter } from "next/navigation";
 import { useAuth } from "../auth-context";
 import { authFormStyles as styles } from "../styles/auth-form";
 import { LanguageSelector } from "../components/LanguageSelector";
+import { useTranslation } from "../hooks/useTranslation";
 
 export default function LoginPage() {
   const [email, setEmail] = useState("");
@@ -13,6 +14,7 @@ export default function LoginPage() {
   const [isSubmitting, setIsSubmitting] = useState(false);
   const { login } = useAuth();
   const router = useRouter();
+  const t = useTranslation("auth");
 
   const handleSubmit = async (e: React.FormEvent) => {
     e.preventDefault();
@@ -23,7 +25,7 @@ export default function LoginPage() {
       await login(email, password);
       router.push("/");
     } catch (err) {
-      setError(err instanceof Error ? err.message : "Login failed");
+      setError(err instanceof Error ? err.message : t("login.loginFailed"));
     } finally {
       setIsSubmitting(false);
     }
@@ -37,8 +39,8 @@ export default function LoginPage() {
       <div style={styles.container}>
         <div style={styles.card}>
           <div style={styles.header}>
-            <h1 style={styles.title}>Welcome back</h1>
-            <p style={styles.subtitle}>Sign in to your account</p>
+            <h1 style={styles.title}>{t("login.title")}</h1>
+            <p style={styles.subtitle}>{t("login.subtitle")}</p>
           </div>
 
           <form onSubmit={handleSubmit} style={styles.form}>
@@ -46,7 +48,7 @@ export default function LoginPage() {
 
             <div style={styles.field}>
               <label htmlFor="email" style={styles.label}>
-                Email
+                {t("login.email")}
               </label>
               <input
                 id="email"
@@ -54,14 +56,14 @@ export default function LoginPage() {
                 value={email}
                 onChange={(e) => setEmail(e.target.value)}
                 style={styles.input}
-                placeholder="you@example.com"
+                placeholder={t("login.emailPlaceholder")}
                 required
               />
             </div>
 
             <div style={styles.field}>
               <label htmlFor="password" style={styles.label}>
-                Password
+                {t("login.password")}
               </label>
               <input
                 id="password"
@@ -69,7 +71,7 @@ export default function LoginPage() {
                 value={password}
                 onChange={(e) => setPassword(e.target.value)}
                 style={styles.input}
-                placeholder="••••••••"
+                placeholder={t("login.passwordPlaceholder")}
                 required
               />
             </div>
@@ -82,14 +84,14 @@ export default function LoginPage() {
               }}
               disabled={isSubmitting}
             >
-              {isSubmitting ? "Signing in..." : "Sign in"}
+              {isSubmitting ? t("login.signingIn") : t("login.signIn")}
             </button>
           </form>
 
           <p style={styles.footer}>
-            Don&apos;t have an account?{" "}
+            {t("login.noAccount")}{" "}
             <a href="/signup" style={styles.link}>
-              Sign up
+              {t("login.signUp")}
             </a>
           </p>
         </div>
diff --git a/frontend/app/signup/[code]/page.tsx b/frontend/app/signup/[code]/page.tsx
index 0505e56..53738f8 100644
--- a/frontend/app/signup/[code]/page.tsx
+++ b/frontend/app/signup/[code]/page.tsx
@@ -4,12 +4,14 @@ import { useEffect } from "react";
 import { useRouter, useParams } from "next/navigation";
 import { useAuth } from "../../auth-context";
 import { LanguageSelector } from "../../components/LanguageSelector";
+import { useTranslation } from "../../hooks/useTranslation";
 
 export default function SignupWithCodePage() {
   const params = useParams();
   const router = useRouter();
   const { user, isLoading } = useAuth();
   const code = params.code as string;
+  const t = useTranslation("auth");
 
   useEffect(() => {
     // Wait for auth check to complete before redirecting
@@ -40,7 +42,7 @@ export default function SignupWithCodePage() {
       <div style={{ position: "absolute", top: "1rem", right: "1rem" }}>
         <LanguageSelector />
       </div>
-      Redirecting...
+      {t("signup.redirecting")}
     </main>
   );
 }
diff --git a/frontend/app/signup/page.test.tsx b/frontend/app/signup/page.test.tsx
index f4aec2a..7eb09e0 100644
--- a/frontend/app/signup/page.test.tsx
+++ b/frontend/app/signup/page.test.tsx
@@ -21,20 +21,20 @@ afterEach(() => cleanup());
 test("renders signup form with title", () => {
   renderWithProviders(<SignupPage />);
   // Step 1 shows "Join with Invite" title (invite code entry)
-  expect(screen.getByRole("heading", { name: "Join with Invite" })).toBeDefined();
+  expect(screen.getByRole("heading", { name: "Únete con Invitación" })).toBeDefined();
 });
 
 test("renders invite code input", () => {
   renderWithProviders(<SignupPage />);
-  expect(screen.getByLabelText("Invite Code")).toBeDefined();
+  expect(screen.getByLabelText("Código de Invitación")).toBeDefined();
 });
 
 test("renders continue button", () => {
   renderWithProviders(<SignupPage />);
-  expect(screen.getByRole("button", { name: "Continue" })).toBeDefined();
+  expect(screen.getByRole("button", { name: "Continuar" })).toBeDefined();
 });
 
 test("renders link to login", () => {
   renderWithProviders(<SignupPage />);
-  expect(screen.getByText("Sign in")).toBeDefined();
+  expect(screen.getByText("Iniciar sesión")).toBeDefined();
 });
diff --git a/frontend/app/signup/page.tsx b/frontend/app/signup/page.tsx
index e9c4717..829e6ce 100644
--- a/frontend/app/signup/page.tsx
+++ b/frontend/app/signup/page.tsx
@@ -6,6 +6,7 @@ import { useAuth } from "../auth-context";
 import { invitesApi } from "../api";
 import { authFormStyles as styles } from "../styles/auth-form";
 import { LanguageSelector } from "../components/LanguageSelector";
+import { useTranslation } from "../hooks/useTranslation";
 
 function SignupContent() {
   const searchParams = useSearchParams();
@@ -25,6 +26,7 @@ function SignupContent() {
 
   const { user, register } = useAuth();
   const router = useRouter();
+  const t = useTranslation("auth");
 
   // Redirect if already logged in
   useEffect(() => {
@@ -51,11 +53,11 @@ function SignupContent() {
         setInviteError("");
       } else {
         setInviteValid(false);
-        setInviteError(response.error || "Invalid invite code");
+        setInviteError(response.error || t("signup.invalidInviteCode"));
       }
     } catch {
       setInviteValid(false);
-      setInviteError("Failed to verify invite code");
+      setInviteError(t("signup.failedToVerify"));
     } finally {
       setIsCheckingInvite(false);
     }
@@ -78,12 +80,12 @@ function SignupContent() {
     setError("");
 
     if (password !== confirmPassword) {
-      setError("Passwords do not match");
+      setError(t("signup.passwordsDoNotMatch"));
       return;
     }
 
     if (password.length < 6) {
-      setError("Password must be at least 6 characters");
+      setError(t("signup.passwordTooShort"));
       return;
     }
 
@@ -93,7 +95,7 @@ function SignupContent() {
       await register(email, password, inviteCode.trim());
       router.push("/");
     } catch (err) {
-      setError(err instanceof Error ? err.message : "Registration failed");
+      setError(err instanceof Error ? err.message : t("signup.registrationFailed"));
     } finally {
       setIsSubmitting(false);
     }
@@ -114,7 +116,7 @@ function SignupContent() {
         <div style={styles.container}>
           <div style={styles.card}>
             <div style={{ textAlign: "center", color: "rgba(255,255,255,0.6)" }}>
-              Checking invite code...
+              {t("signup.checkingInviteCode")}
             </div>
           </div>
         </div>
@@ -132,8 +134,8 @@ function SignupContent() {
         <div style={styles.container}>
           <div style={styles.card}>
             <div style={styles.header}>
-              <h1 style={styles.title}>Join with Invite</h1>
-              <p style={styles.subtitle}>Enter your invite code to get started</p>
+              <h1 style={styles.title}>{t("signup.title")}</h1>
+              <p style={styles.subtitle}>{t("signup.subtitle")}</p>
             </div>
 
             <form onSubmit={handleInviteSubmit} style={styles.form}>
@@ -141,7 +143,7 @@ function SignupContent() {
 
               <div style={styles.field}>
                 <label htmlFor="inviteCode" style={styles.label}>
-                  Invite Code
+                  {t("signup.inviteCode")}
                 </label>
                 <input
                   id="inviteCode"
@@ -153,7 +155,7 @@ function SignupContent() {
                     setInviteValid(null);
                   }}
                   style={styles.input}
-                  placeholder="word-word-00"
+                  placeholder={t("signup.inviteCodePlaceholder")}
                   required
                   autoFocus
                 />
@@ -165,7 +167,7 @@ function SignupContent() {
                     display: "block",
                   }}
                 >
-                  Ask your inviter for this code
+                  {t("signup.inviteHint")}
                 </span>
               </div>
 
@@ -177,14 +179,14 @@ function SignupContent() {
                 }}
                 disabled={isCheckingInvite || !inviteCode.trim()}
               >
-                {isCheckingInvite ? "Checking..." : "Continue"}
+                {isCheckingInvite ? t("signup.checking") : t("signup.continue")}
               </button>
             </form>
 
             <p style={styles.footer}>
-              Already have an account?{" "}
+              {t("signup.alreadyHaveAccount")}{" "}
               <a href="/login" style={styles.link}>
-                Sign in
+                {t("signup.signIn")}
               </a>
             </p>
           </div>
@@ -202,9 +204,9 @@ function SignupContent() {
       <div style={styles.container}>
         <div style={styles.card}>
           <div style={styles.header}>
-            <h1 style={styles.title}>Create account</h1>
+            <h1 style={styles.title}>{t("signup.createAccountTitle")}</h1>
             <p style={styles.subtitle}>
-              Using invite:{" "}
+              {t("signup.createAccountSubtitle")}{" "}
               <code
                 style={{
                   background: "rgba(255,255,255,0.1)",
@@ -223,7 +225,7 @@ function SignupContent() {
 
             <div style={styles.field}>
               <label htmlFor="email" style={styles.label}>
-                Email
+                {t("signup.email")}
               </label>
               <input
                 id="email"
@@ -231,7 +233,7 @@ function SignupContent() {
                 value={email}
                 onChange={(e) => setEmail(e.target.value)}
                 style={styles.input}
-                placeholder="you@example.com"
+                placeholder={t("signup.emailPlaceholder")}
                 required
                 autoFocus
               />
@@ -239,7 +241,7 @@ function SignupContent() {
 
             <div style={styles.field}>
               <label htmlFor="password" style={styles.label}>
-                Password
+                {t("signup.password")}
               </label>
               <input
                 id="password"
@@ -247,14 +249,14 @@ function SignupContent() {
                 value={password}
                 onChange={(e) => setPassword(e.target.value)}
                 style={styles.input}
-                placeholder="••••••••"
+                placeholder={t("signup.passwordPlaceholder")}
                 required
               />
             </div>
 
             <div style={styles.field}>
               <label htmlFor="confirmPassword" style={styles.label}>
-                Confirm Password
+                {t("signup.confirmPassword")}
               </label>
               <input
                 id="confirmPassword"
@@ -262,7 +264,7 @@ function SignupContent() {
                 value={confirmPassword}
                 onChange={(e) => setConfirmPassword(e.target.value)}
                 style={styles.input}
-                placeholder="••••••••"
+                placeholder={t("signup.confirmPasswordPlaceholder")}
                 required
               />
             </div>
@@ -275,7 +277,7 @@ function SignupContent() {
               }}
               disabled={isSubmitting}
             >
-              {isSubmitting ? "Creating account..." : "Create account"}
+              {isSubmitting ? t("signup.creatingAccount") : t("signup.createAccount")}
             </button>
           </form>
 
@@ -293,7 +295,7 @@ function SignupContent() {
                 padding: 0,
               }}
             >
-              Use a different invite code
+              {t("signup.useDifferentCode")}
             </button>
           </p>
         </div>
diff --git a/frontend/locales/ca/auth.json b/frontend/locales/ca/auth.json
new file mode 100644
index 0000000..7e4ac0a
--- /dev/null
+++ b/frontend/locales/ca/auth.json
@@ -0,0 +1,44 @@
+{
+  "login": {
+    "title": "Benvingut de nou",
+    "subtitle": "Inicia sessió al teu compte",
+    "email": "Correu electrònic",
+    "password": "Contrasenya",
+    "emailPlaceholder": "tu@exemple.com",
+    "passwordPlaceholder": "••••••••",
+    "signIn": "Iniciar sessió",
+    "signingIn": "Iniciant sessió...",
+    "noAccount": "No tens un compte?",
+    "signUp": "Registra't",
+    "loginFailed": "Error en iniciar sessió"
+  },
+  "signup": {
+    "title": "Uneix-te amb Invitació",
+    "subtitle": "Introdueix el teu codi d'invitació per començar",
+    "inviteCode": "Codi d'Invitació",
+    "inviteCodePlaceholder": "paraula-paraula-00",
+    "inviteHint": "Demana aquest codi al teu convidant",
+    "checking": "Comprovant...",
+    "continue": "Continuar",
+    "checkingInviteCode": "Comprovant codi d'invitació...",
+    "createAccount": "Crear compte",
+    "createAccountTitle": "Crear compte",
+    "createAccountSubtitle": "Utilitzant invitació:",
+    "email": "Correu electrònic",
+    "emailPlaceholder": "tu@exemple.com",
+    "password": "Contrasenya",
+    "passwordPlaceholder": "••••••••",
+    "confirmPassword": "Confirmar Contrasenya",
+    "confirmPasswordPlaceholder": "••••••••",
+    "creatingAccount": "Creant compte...",
+    "alreadyHaveAccount": "Ja tens un compte?",
+    "signIn": "Iniciar sessió",
+    "useDifferentCode": "Utilitzar un codi d'invitació diferent",
+    "redirecting": "Redirigint...",
+    "passwordsDoNotMatch": "Les contrasenyes no coincideixen",
+    "passwordTooShort": "La contrasenya ha de tenir almenys 6 caràcters",
+    "invalidInviteCode": "Codi d'invitació invàlid",
+    "failedToVerify": "Error en verificar codi d'invitació",
+    "registrationFailed": "Error en registrar-se"
+  }
+}
diff --git a/frontend/locales/en/auth.json b/frontend/locales/en/auth.json
new file mode 100644
index 0000000..fd5b9cd
--- /dev/null
+++ b/frontend/locales/en/auth.json
@@ -0,0 +1,44 @@
+{
+  "login": {
+    "title": "Welcome back",
+    "subtitle": "Sign in to your account",
+    "email": "Email",
+    "password": "Password",
+    "emailPlaceholder": "you@example.com",
+    "passwordPlaceholder": "••••••••",
+    "signIn": "Sign in",
+    "signingIn": "Signing in...",
+    "noAccount": "Don't have an account?",
+    "signUp": "Sign up",
+    "loginFailed": "Login failed"
+  },
+  "signup": {
+    "title": "Join with Invite",
+    "subtitle": "Enter your invite code to get started",
+    "inviteCode": "Invite Code",
+    "inviteCodePlaceholder": "word-word-00",
+    "inviteHint": "Ask your inviter for this code",
+    "checking": "Checking...",
+    "continue": "Continue",
+    "checkingInviteCode": "Checking invite code...",
+    "createAccount": "Create account",
+    "createAccountTitle": "Create account",
+    "createAccountSubtitle": "Using invite:",
+    "email": "Email",
+    "emailPlaceholder": "you@example.com",
+    "password": "Password",
+    "passwordPlaceholder": "••••••••",
+    "confirmPassword": "Confirm Password",
+    "confirmPasswordPlaceholder": "••••••••",
+    "creatingAccount": "Creating account...",
+    "alreadyHaveAccount": "Already have an account?",
+    "signIn": "Sign in",
+    "useDifferentCode": "Use a different invite code",
+    "redirecting": "Redirecting...",
+    "passwordsDoNotMatch": "Passwords do not match",
+    "passwordTooShort": "Password must be at least 6 characters",
+    "invalidInviteCode": "Invalid invite code",
+    "failedToVerify": "Failed to verify invite code",
+    "registrationFailed": "Registration failed"
+  }
+}
diff --git a/frontend/locales/es/auth.json b/frontend/locales/es/auth.json
new file mode 100644
index 0000000..39be272
--- /dev/null
+++ b/frontend/locales/es/auth.json
@@ -0,0 +1,44 @@
+{
+  "login": {
+    "title": "Bienvenido de nuevo",
+    "subtitle": "Inicia sesión en tu cuenta",
+    "email": "Correo electrónico",
+    "password": "Contraseña",
+    "emailPlaceholder": "tu@ejemplo.com",
+    "passwordPlaceholder": "••••••••",
+    "signIn": "Iniciar sesión",
+    "signingIn": "Iniciando sesión...",
+    "noAccount": "¿No tienes una cuenta?",
+    "signUp": "Regístrate",
+    "loginFailed": "Error al iniciar sesión"
+  },
+  "signup": {
+    "title": "Únete con Invitación",
+    "subtitle": "Ingresa tu código de invitación para comenzar",
+    "inviteCode": "Código de Invitación",
+    "inviteCodePlaceholder": "palabra-palabra-00",
+    "inviteHint": "Pide este código a tu invitador",
+    "checking": "Verificando...",
+    "continue": "Continuar",
+    "checkingInviteCode": "Verificando código de invitación...",
+    "createAccount": "Crear cuenta",
+    "createAccountTitle": "Crear cuenta",
+    "createAccountSubtitle": "Usando invitación:",
+    "email": "Correo electrónico",
+    "emailPlaceholder": "tu@ejemplo.com",
+    "password": "Contraseña",
+    "passwordPlaceholder": "••••••••",
+    "confirmPassword": "Confirmar Contraseña",
+    "confirmPasswordPlaceholder": "••••••••",
+    "creatingAccount": "Creando cuenta...",
+    "alreadyHaveAccount": "¿Ya tienes una cuenta?",
+    "signIn": "Iniciar sesión",
+    "useDifferentCode": "Usar un código de invitación diferente",
+    "redirecting": "Redirigiendo...",
+    "passwordsDoNotMatch": "Las contraseñas no coinciden",
+    "passwordTooShort": "La contraseña debe tener al menos 6 caracteres",
+    "invalidInviteCode": "Código de invitación inválido",
+    "failedToVerify": "Error al verificar código de invitación",
+    "registrationFailed": "Error al registrarse"
+  }
+}