diff --git a/src/components/admin/admin-layout.tsx b/src/components/admin/admin-layout.tsx
index 61cf674..fffa719 100644
--- a/src/components/admin/admin-layout.tsx
+++ b/src/components/admin/admin-layout.tsx
@@ -24,6 +24,7 @@ import {
   UserCog,
   Bell,
 } from 'lucide-react';
+import { ThemeToggle } from '@/components/theme/theme-toggle';
 
 const menuItems = [
   {
@@ -264,6 +265,7 @@ export function AdminLayout({ children }: { children: React.ReactNode }) {
           <div className="flex-1" />
 
           <div className="flex items-center gap-4">
+            <ThemeToggle />
             <Link
               href="/"
               target="_blank"
diff --git a/src/components/layout/header.tsx b/src/components/layout/header.tsx
index 5738a88..f71bd04 100644
--- a/src/components/layout/header.tsx
+++ b/src/components/layout/header.tsx
@@ -11,6 +11,7 @@ import { useSiteConfig, type NavigationItem } from '@/lib/site-config';
 import { MegaDropdown } from '@/components/layout/mega-dropdown';
 import { useFocusTrap } from '@/hooks/use-focus-trap';
 import { cn } from '@/lib/utils';
+import { ThemeToggle } from '@/components/theme/theme-toggle';
 
 function HeaderContent() {
   const [isOpen, setIsOpen] = useState(false);
@@ -153,6 +154,7 @@ function HeaderContent() {
             </nav>
 
             <div className="hidden md:flex items-center gap-3">
+              <ThemeToggle />
               <Button
                 size="sm"
                 asChild
diff --git a/src/components/theme/theme-toggle.tsx b/src/components/theme/theme-toggle.tsx
new file mode 100644
index 0000000..f136ee6
--- /dev/null
+++ b/src/components/theme/theme-toggle.tsx
@@ -0,0 +1,87 @@
+'use client';
+
+import { useEffect, useState } from 'react';
+import { Sun, Moon } from 'lucide-react';
+import { cn } from '@/lib/utils';
+
+type Theme = 'light' | 'dark';
+
+const STORAGE_KEY = 'novalon-theme';
+
+/**
+ * 读取当前应生效的主题：
+ * 1. 优先用用户显式选择（localStorage，与 layout.tsx FOUC 脚本同一 key）
+ * 2. 回退到 FOUC 脚本已同步写入 <html data-theme> 的值
+ * 3. 默认浅色
+ * 这样即便用户刷新，状态也与首帧 FOUC 脚本完全一致，无闪烁。
+ */
+function resolveTheme(): Theme {
+  if (typeof window === 'undefined') return 'light';
+  const stored = window.localStorage.getItem(STORAGE_KEY);
+  if (stored === 'light' || stored === 'dark') return stored;
+  const attr = document.documentElement.getAttribute('data-theme');
+  if (attr === 'light' || attr === 'dark') return attr as Theme;
+  return 'light';
+}
+
+function applyTheme(theme: Theme) {
+  document.documentElement.setAttribute('data-theme', theme);
+  try {
+    window.localStorage.setItem(STORAGE_KEY, theme);
+  } catch {
+    /* 隐私模式等写入失败时忽略：仅本次会话生效 */
+  }
+}
+
+export function ThemeToggle({ className }: { className?: string }) {
+  // 初始为 null，挂载后再解析真实主题，避免 SSR/CSR 水合不一致
+  const [theme, setTheme] = useState<Theme | null>(null);
+  const [mounted, setMounted] = useState(false);
+
+  // 必须挂载后读取：FOUC 脚本已在 <head> 同步写入 data-theme，
+  // 此处从 DOM/localStorage 还原真实主题。SSR 阶段 window 不可用，
+  // 故无法用 useState 惰性初始化（否则首帧与客户端水合不一致）。
+  useEffect(() => {
+    // 主题同步必须从挂载后 DOM 读取，此 setState 无法避免
+    // eslint-disable-next-line react-hooks/set-state-in-effect
+    setTheme(resolveTheme());
+    setMounted(true);
+  }, []);
+
+  const isDark = theme === 'dark';
+
+  const toggle = () => {
+    const next: Theme = isDark ? 'light' : 'dark';
+    setTheme(next);
+    applyTheme(next);
+  };
+
+  return (
+    <button
+      type="button"
+      onClick={toggle}
+      aria-label={isDark ? '切换到浅色模式' : '切换到暗黑模式'}
+      aria-pressed={isDark}
+      className={cn(
+        'inline-flex items-center justify-center w-9 h-9 rounded-lg border border-border-primary',
+        'text-text-tertiary hover:text-text-primary hover:bg-bg-hover',
+        'transition-colors duration-200 ease-ink',
+        'focus:outline-none focus-visible:ring-2 focus-visible:ring-border-dark',
+        className,
+      )}
+    >
+      {/* 挂载前渲染占位，避免与 FOUC 已应用的主题产生水合差异 */}
+      {mounted ? (
+        isDark ? (
+          <Moon className="w-4 h-4" aria-hidden="true" />
+        ) : (
+          <Sun className="w-4 h-4" aria-hidden="true" />
+        )
+      ) : (
+        <span className="block w-4 h-4" aria-hidden="true" />
+      )}
+    </button>
+  );
+}
+
+export default ThemeToggle;
