diff --git a/src/components/Navbar.jsx b/src/components/Navbar.jsx
index 5e205a8..f3f4a7d 100644
--- a/src/components/Navbar.jsx
+++ b/src/components/Navbar.jsx
@@ -1,8 +1,10 @@
 import { useState } from 'react';
 import { NAV_LINKS, BRAND } from '../data/navigation';
+import { useTheme } from '../context/ThemeContext';
 
 function Navbar() {
     const [menuOpen, setMenuOpen] = useState(false);
+    const { theme, toggleTheme } = useTheme();
 
     return (
         <header className="navbar" role="banner">
@@ -39,6 +41,15 @@ function Navbar() {
                             </li>
                         ))}
                     </ul>
+                    <button
+                        type="button"
+                        className="navbar__theme-toggle"
+                        onClick={toggleTheme}
+                        aria-label={theme === 'dark' ? '切換為淺色主題' : '切換為深色主題'}
+                        title={theme === 'dark' ? '淺色模式' : '深色模式'}
+                    >
+                        {theme === 'dark' ? '☀️' : '🌙'}
+                    </button>
                     <a href="#demo" className="btn btn--primary btn--sm navbar__cta">
                         預約 Demo
                     </a>
diff --git a/src/context/ThemeContext.jsx b/src/context/ThemeContext.jsx
new file mode 100644
index 0000000..a64116f
--- /dev/null
+++ b/src/context/ThemeContext.jsx
@@ -0,0 +1,31 @@
+import { createContext, useContext, useEffect, useState } from 'react';
+
+const STORAGE_KEY = 'salespilot-theme';
+
+const ThemeContext = createContext(null);
+
+export function ThemeProvider({ children }) {
+    const [theme, setThemeState] = useState(() => {
+        if (typeof window === 'undefined') return 'dark';
+        return window.localStorage.getItem(STORAGE_KEY) || 'dark';
+    });
+
+    useEffect(() => {
+        document.documentElement.setAttribute('data-theme', theme);
+        window.localStorage.setItem(STORAGE_KEY, theme);
+    }, [theme]);
+
+    const toggleTheme = () => setThemeState((t) => (t === 'dark' ? 'light' : 'dark'));
+
+    return (
+        <ThemeContext.Provider value={{ theme, setTheme: setThemeState, toggleTheme }}>
+            {children}
+        </ThemeContext.Provider>
+    );
+}
+
+export function useTheme() {
+    const ctx = useContext(ThemeContext);
+    if (!ctx) throw new Error('useTheme must be used within ThemeProvider');
+    return ctx;
+}
diff --git a/src/index.css b/src/index.css
index 507bc0c..71a23e7 100644
--- a/src/index.css
+++ b/src/index.css
@@ -82,6 +82,38 @@
   /* Layout */
   --container-max: 1200px;
   --navbar-height: 72px;
+
+  /* Navbar overlay (for theme) */
+  --navbar-bg: rgba(10, 14, 26, 0.8);
+}
+
+/* --- 淺色主題 --- */
+[data-theme="light"] {
+  --color-bg: #f8fafc;
+  --color-bg-elevated: #ffffff;
+  --color-bg-card: #ffffff;
+  --color-bg-card-hover: #f1f5f9;
+  --color-surface: #e2e8f0;
+
+  --color-primary: #4f46e5;
+  --color-primary-light: #6366f1;
+  --color-primary-dark: #4338ca;
+  --color-primary-glow: rgba(79, 70, 229, 0.2);
+
+  --color-text: #0f172a;
+  --color-text-secondary: #475569;
+  --color-text-muted: #64748b;
+  --color-text-inverse: #f1f5f9;
+
+  --color-border: rgba(15, 23, 42, 0.12);
+  --color-border-hover: rgba(15, 23, 42, 0.25);
+
+  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.06);
+  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
+  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.1);
+  --shadow-glow: 0 0 40px var(--color-primary-glow);
+
+  --navbar-bg: rgba(248, 250, 252, 0.9);
 }
 
 /* --- Reset & Base --- */
@@ -256,7 +288,7 @@ button {
   right: 0;
   height: var(--navbar-height);
   z-index: 1000;
-  background: rgba(10, 14, 26, 0.8);
+  background: var(--navbar-bg);
   backdrop-filter: blur(16px);
   border-bottom: 1px solid var(--color-border);
 }
@@ -292,6 +324,24 @@ button {
   gap: var(--space-6);
 }
 
+.navbar__theme-toggle {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 2.5rem;
+  height: 2.5rem;
+  border-radius: var(--radius-md);
+  background: var(--color-surface);
+  color: var(--color-text);
+  font-size: 1.25rem;
+  transition: background var(--transition-fast), transform var(--transition-fast);
+}
+
+.navbar__theme-toggle:hover {
+  background: var(--color-border-hover);
+  transform: scale(1.05);
+}
+
 .navbar__link {
   font-size: var(--text-sm);
   font-weight: 500;
@@ -367,6 +417,10 @@ button {
     font-size: var(--text-lg);
   }
 
+  .navbar__theme-toggle {
+    margin-top: var(--space-4);
+  }
+
   .navbar__cta {
     width: 100%;
     margin-top: var(--space-4);
diff --git a/src/main.jsx b/src/main.jsx
index 644bee6..167b005 100644
--- a/src/main.jsx
+++ b/src/main.jsx
@@ -1,10 +1,13 @@
 import React from 'react';
 import ReactDOM from 'react-dom/client';
 import App from './App';
+import { ThemeProvider } from './context/ThemeContext';
 import './index.css';
 
 ReactDOM.createRoot(document.getElementById('root')).render(
     <React.StrictMode>
-        <App />
+        <ThemeProvider>
+            <App />
+        </ThemeProvider>
     </React.StrictMode>,
 );