diff --git a/.claude/skills/component/references/videojs.md b/.claude/skills/component/references/videojs.md
index 4c9316e0..8cb17752 100644
--- a/.claude/skills/component/references/videojs.md
+++ b/.claude/skills/component/references/videojs.md
@@ -46,11 +46,19 @@ interface PlayButtonProps {
 ### State Interface
 
 ```ts
+// When keys match the feature state, use Pick (preserves JSDoc on IDE hover)
 interface PlayButtonState extends Pick<PlaybackState, 'paused' | 'ended' | 'started'> {}
+
+// When renaming keys, use Pick for matching keys and add JSDoc for renamed ones
+interface FullscreenButtonState extends Pick<FullscreenState, 'fullscreen'> {
+  /** Whether fullscreen can be requested on this platform. */
+  availability: FullscreenState['fullscreenAvailability'];
+}
 ```
 
 - Primitives only — no methods
-- Use `Pick<FeatureState, ...>` to select relevant fields
+- Use `Pick<FeatureState, ...>` to select relevant fields — preserves JSDoc on IDE hover
+- When a key is renamed for the button context, use `FeatureState['...']` for the type and add a JSDoc description
 
 ### Core Class
 
@@ -226,6 +234,8 @@ packages/
     └── utils/                            # renderElement, mergeProps
 ```
 
+**No barrel exports for simple components** — Don't create `index.ts` files for simple UI components. Export directly from individual files. Reserve `index.ts` barrels for compound components with multiple related exports that form a cohesive API.
+
 ---
 
 ## Component Registration
diff --git a/packages/core/src/core/index.ts b/packages/core/src/core/index.ts
index 56e74cb6..ad0035ef 100644
--- a/packages/core/src/core/index.ts
+++ b/packages/core/src/core/index.ts
@@ -1,5 +1,7 @@
 export * from './element';
 export * from './media/state';
+export * from './ui/fullscreen-button/fullscreen-button-core';
+export * from './ui/fullscreen-button/fullscreen-button-data-attrs';
 export * from './ui/mute-button/mute-button-core';
 export * from './ui/mute-button/mute-button-data-attrs';
 export * from './ui/play-button/play-button-core';
diff --git a/packages/core/src/core/ui/fullscreen-button/fullscreen-button-core.test.ts b/packages/core/src/core/ui/fullscreen-button/fullscreen-button-core.test.ts
new file mode 100644
index 00000000..30ce115f
--- /dev/null
+++ b/packages/core/src/core/ui/fullscreen-button/fullscreen-button-core.test.ts
@@ -0,0 +1,158 @@
+import { describe, expect, it, vi } from 'vitest';
+
+import type { FullscreenState } from '../../media/state';
+import { FullscreenButtonCore } from './fullscreen-button-core';
+
+function createMockFullscreen(overrides: Partial<FullscreenState> = {}): FullscreenState {
+  return {
+    fullscreen: false,
+    fullscreenAvailability: 'available',
+    requestFullscreen: vi.fn(),
+    exitFullscreen: vi.fn(),
+    ...overrides,
+  };
+}
+
+describe('FullscreenButtonCore', () => {
+  describe('getLabel', () => {
+    it('returns custom label string when provided', () => {
+      const core = new FullscreenButtonCore({ label: 'Custom Label' });
+      const state = createMockFullscreen();
+
+      expect(core.getLabel(state)).toBe('Custom Label');
+    });
+
+    it('returns custom label from function when provided', () => {
+      const core = new FullscreenButtonCore({
+        label: (state) => (state.fullscreen ? 'Exit' : 'Enter'),
+      });
+      const state = createMockFullscreen({ fullscreen: true });
+
+      expect(core.getLabel(state)).toBe('Exit');
+    });
+
+    it('falls back to default label when function returns empty string', () => {
+      const core = new FullscreenButtonCore({ label: () => '' });
+      const state = createMockFullscreen({ fullscreen: false });
+
+      expect(core.getLabel(state)).toBe('Enter fullscreen');
+    });
+
+    it('returns "Exit fullscreen" when active', () => {
+      const core = new FullscreenButtonCore();
+      const state = createMockFullscreen({ fullscreen: true });
+
+      expect(core.getLabel(state)).toBe('Exit fullscreen');
+    });
+
+    it('returns "Enter fullscreen" when not active', () => {
+      const core = new FullscreenButtonCore();
+      const state = createMockFullscreen({ fullscreen: false });
+
+      expect(core.getLabel(state)).toBe('Enter fullscreen');
+    });
+  });
+
+  describe('getAttrs', () => {
+    it('returns aria-label based on fullscreen state', () => {
+      const core = new FullscreenButtonCore();
+      const state = createMockFullscreen({ fullscreen: true });
+
+      const attrs = core.getAttrs(state);
+
+      expect(attrs['aria-label']).toBe('Exit fullscreen');
+    });
+
+    it('returns aria-disabled when disabled', () => {
+      const core = new FullscreenButtonCore({ disabled: true });
+      const state = createMockFullscreen();
+
+      const attrs = core.getAttrs(state);
+
+      expect(attrs['aria-disabled']).toBe('true');
+    });
+
+    it('returns undefined aria-disabled when not disabled', () => {
+      const core = new FullscreenButtonCore({ disabled: false });
+      const state = createMockFullscreen();
+
+      const attrs = core.getAttrs(state);
+
+      expect(attrs['aria-disabled']).toBeUndefined();
+    });
+  });
+
+  describe('getState', () => {
+    it('returns primitive values only (no methods)', () => {
+      const core = new FullscreenButtonCore();
+      const state = createMockFullscreen({ fullscreen: true });
+
+      const buttonState = core.getState(state);
+
+      expect(buttonState).toEqual({
+        fullscreen: true,
+        availability: 'available',
+      });
+
+      const functionKeys = Object.entries(buttonState).filter(([, value]) => typeof value === 'function');
+      expect(functionKeys).toHaveLength(0);
+    });
+
+    it('picks fullscreen from state', () => {
+      const core = new FullscreenButtonCore();
+
+      expect(core.getState(createMockFullscreen({ fullscreen: true })).fullscreen).toBe(true);
+      expect(core.getState(createMockFullscreen({ fullscreen: false })).fullscreen).toBe(false);
+    });
+
+    it('picks availability from state', () => {
+      const core = new FullscreenButtonCore();
+
+      expect(core.getState(createMockFullscreen({ fullscreenAvailability: 'unsupported' })).availability).toBe(
+        'unsupported'
+      );
+    });
+  });
+
+  describe('toggle', () => {
+    it('calls requestFullscreen when not active', async () => {
+      const core = new FullscreenButtonCore();
+      const state = createMockFullscreen({ fullscreen: false });
+
+      await core.toggle(state);
+
+      expect(state.requestFullscreen).toHaveBeenCalledTimes(1);
+      expect(state.exitFullscreen).not.toHaveBeenCalled();
+    });
+
+    it('calls exitFullscreen when active', async () => {
+      const core = new FullscreenButtonCore();
+      const state = createMockFullscreen({ fullscreen: true });
+
+      await core.toggle(state);
+
+      expect(state.exitFullscreen).toHaveBeenCalledTimes(1);
+      expect(state.requestFullscreen).not.toHaveBeenCalled();
+    });
+
+    it('does nothing when disabled', async () => {
+      const core = new FullscreenButtonCore({ disabled: true });
+      const state = createMockFullscreen();
+
+      await core.toggle(state);
+
+      expect(state.requestFullscreen).not.toHaveBeenCalled();
+      expect(state.exitFullscreen).not.toHaveBeenCalled();
+    });
+
+    it('does nothing when availability is not available', async () => {
+      const core = new FullscreenButtonCore();
+      const state = createMockFullscreen({ fullscreenAvailability: 'unsupported' });
+
+      await core.toggle(state);
+
+      expect(state.requestFullscreen).not.toHaveBeenCalled();
+      expect(state.exitFullscreen).not.toHaveBeenCalled();
+    });
+  });
+});
diff --git a/packages/core/src/core/ui/fullscreen-button/fullscreen-button-core.ts b/packages/core/src/core/ui/fullscreen-button/fullscreen-button-core.ts
new file mode 100644
index 00000000..dd7faccb
--- /dev/null
+++ b/packages/core/src/core/ui/fullscreen-button/fullscreen-button-core.ts
@@ -0,0 +1,83 @@
+import { defaults } from '@videojs/utils/object';
+import { isFunction } from '@videojs/utils/predicate';
+import type { NonNullableObject } from '@videojs/utils/types';
+
+import type { ElementProps } from '../../element';
+import type { FullscreenState } from '../../media/state';
+
+export interface FullscreenButtonProps {
+  /** Custom label for the button. */
+  label?: string | ((state: FullscreenButtonState) => string) | undefined;
+  /** Whether the button is disabled. */
+  disabled?: boolean | undefined;
+}
+
+export interface FullscreenButtonState extends Pick<FullscreenState, 'fullscreen'> {
+  /** Whether fullscreen can be requested on this platform. */
+  availability: FullscreenState['fullscreenAvailability'];
+}
+
+export class FullscreenButtonCore {
+  static readonly defaultProps: NonNullableObject<FullscreenButtonProps> = {
+    label: '',
+    disabled: false,
+  };
+
+  #props = { ...FullscreenButtonCore.defaultProps };
+
+  constructor(props?: FullscreenButtonProps) {
+    if (props) this.setProps(props);
+  }
+
+  setProps(props: FullscreenButtonProps): void {
+    this.#props = defaults(props, FullscreenButtonCore.defaultProps);
+  }
+
+  getLabel(state: FullscreenState): string {
+    const buttonState = this.getState(state);
+    const { label } = this.#props;
+
+    if (isFunction(label)) {
+      const customLabel = label(buttonState);
+      if (customLabel) return customLabel;
+    } else if (label) {
+      return label;
+    }
+
+    return buttonState.fullscreen ? 'Exit fullscreen' : 'Enter fullscreen';
+  }
+
+  getAttrs(state: FullscreenState): ElementProps {
+    return {
+      'aria-label': this.getLabel(state),
+      'aria-disabled': this.#props.disabled ? 'true' : undefined,
+    };
+  }
+
+  getState(state: FullscreenState): FullscreenButtonState {
+    return {
+      fullscreen: state.fullscreen,
+      availability: state.fullscreenAvailability,
+    };
+  }
+
+  async toggle(state: FullscreenState): Promise<void> {
+    if (this.#props.disabled) return;
+    if (state.fullscreenAvailability !== 'available') return;
+
+    try {
+      if (state.fullscreen) {
+        await state.exitFullscreen();
+      } else {
+        await state.requestFullscreen();
+      }
+    } catch {
+      // Fullscreen requests can fail (user gesture required, permissions, etc.)
+    }
+  }
+}
+
+export namespace FullscreenButtonCore {
+  export type Props = FullscreenButtonProps;
+  export type State = FullscreenButtonState;
+}
diff --git a/packages/core/src/core/ui/fullscreen-button/fullscreen-button-data-attrs.ts b/packages/core/src/core/ui/fullscreen-button/fullscreen-button-data-attrs.ts
new file mode 100644
index 00000000..d194d2f9
--- /dev/null
+++ b/packages/core/src/core/ui/fullscreen-button/fullscreen-button-data-attrs.ts
@@ -0,0 +1,6 @@
+export const FullscreenButtonDataAttributes = {
+  /** Present when fullscreen mode is active. */
+  fullscreen: 'data-fullscreen',
+  /** Indicates fullscreen availability (`available` or `unsupported`). */
+  availability: 'data-availability',
+} as const;
diff --git a/packages/html/src/define/ui/fullscreen-button.ts b/packages/html/src/define/ui/fullscreen-button.ts
new file mode 100644
index 00000000..5f497a62
--- /dev/null
+++ b/packages/html/src/define/ui/fullscreen-button.ts
@@ -0,0 +1,9 @@
+import { FullscreenButtonElement } from '../../ui/fullscreen-button/fullscreen-button-element';
+
+customElements.define(FullscreenButtonElement.tagName, FullscreenButtonElement);
+
+declare global {
+  interface HTMLElementTagNameMap {
+    [FullscreenButtonElement.tagName]: FullscreenButtonElement;
+  }
+}
diff --git a/packages/html/src/index.ts b/packages/html/src/index.ts
index 0499a46c..3843738b 100644
--- a/packages/html/src/index.ts
+++ b/packages/html/src/index.ts
@@ -13,11 +13,10 @@ export * from './player/player-mixin';
 export * from './store/container-mixin';
 export * from './store/provider-mixin';
 export * from './store/types';
-
+// UI Components
+export { FullscreenButtonElement } from './ui/fullscreen-button/fullscreen-button-element';
 // Primitives
 export * from './ui/media-element';
-
-// UI Components
 export { MuteButtonElement } from './ui/mute-button/mute-button-element';
 export { PlayButtonElement } from './ui/play-button/play-button-element';
 export { TimeElement } from './ui/time/time-element';
diff --git a/packages/html/src/ui/fullscreen-button/fullscreen-button-element.ts b/packages/html/src/ui/fullscreen-button/fullscreen-button-element.ts
new file mode 100644
index 00000000..654813ca
--- /dev/null
+++ b/packages/html/src/ui/fullscreen-button/fullscreen-button-element.ts
@@ -0,0 +1,71 @@
+import type { PropertyValues } from '@lit/reactive-element';
+import { FullscreenButtonCore } from '@videojs/core';
+import {
+  applyElementProps,
+  applyStateDataAttrs,
+  createButton,
+  logMissingFeature,
+  selectFullscreen,
+} from '@videojs/core/dom';
+
+import { playerContext } from '../../player/context';
+import { PlayerController } from '../../player/player-controller';
+import { MediaElement } from '../media-element';
+
+export class FullscreenButtonElement extends MediaElement {
+  static readonly tagName = 'media-fullscreen-button';
+
+  static override properties = {
+    label: { type: String },
+    disabled: { type: Boolean },
+  };
+
+  label = '';
+  disabled = false;
+
+  readonly #core = new FullscreenButtonCore();
+  readonly #state = new PlayerController(this, playerContext, selectFullscreen);
+
+  #disconnect: AbortController | null = null;
+
+  override connectedCallback(): void {
+    super.connectedCallback();
+
+    this.#disconnect = new AbortController();
+
+    const buttonProps = createButton({
+      onActivate: () => this.#core.toggle(this.#state.value!),
+      isDisabled: () => this.disabled || !this.#state.value,
+    });
+
+    applyElementProps(this, buttonProps, this.#disconnect.signal);
+
+    if (!this.#state.value) {
+      logMissingFeature(FullscreenButtonElement.tagName, 'fullscreen');
+    }
+  }
+
+  override disconnectedCallback(): void {
+    super.disconnectedCallback();
+    this.#disconnect?.abort();
+    this.#disconnect = null;
+  }
+
+  protected override willUpdate(changed: PropertyValues): void {
+    super.willUpdate(changed);
+    this.#core.setProps(this);
+  }
+
+  protected override update(changed: PropertyValues): void {
+    super.update(changed);
+
+    const state = this.#state.value;
+
+    if (!state) {
+      return;
+    }
+
+    applyElementProps(this, this.#core.getAttrs(state));
+    applyStateDataAttrs(this, this.#core.getState(state));
+  }
+}
diff --git a/packages/react/src/index.ts b/packages/react/src/index.ts
index cf3b8b97..5ba369b3 100644
--- a/packages/react/src/index.ts
+++ b/packages/react/src/index.ts
@@ -29,10 +29,9 @@ export {
   type ProviderProps,
 } from './player/create-player';
 
-// UI Hooks
+// UI
+export { FullscreenButton, type FullscreenButtonProps } from './ui/fullscreen-button/fullscreen-button';
 export { useButton } from './ui/hooks/use-button';
-
-// UI Components
 export { MuteButton, type MuteButtonProps } from './ui/mute-button/mute-button';
 export { PlayButton, type PlayButtonProps } from './ui/play-button/play-button';
 export { Time } from './ui/time';
diff --git a/packages/react/src/ui/fullscreen-button/fullscreen-button.tsx b/packages/react/src/ui/fullscreen-button/fullscreen-button.tsx
new file mode 100644
index 00000000..473f0aea
--- /dev/null
+++ b/packages/react/src/ui/fullscreen-button/fullscreen-button.tsx
@@ -0,0 +1,53 @@
+'use client';
+
+import { FullscreenButtonCore } from '@videojs/core';
+import { logMissingFeature, selectFullscreen } from '@videojs/core/dom';
+import type { ForwardedRef } from 'react';
+import { forwardRef, useState } from 'react';
+
+import { usePlayer } from '../../player/context';
+import type { UIComponentProps } from '../../utils/types';
+import { renderElement } from '../../utils/use-render';
+import { useButton } from '../hooks/use-button';
+
+export interface FullscreenButtonProps
+  extends UIComponentProps<'button', FullscreenButtonCore.State>,
+    FullscreenButtonCore.Props {}
+
+export const FullscreenButton = forwardRef(function FullscreenButton(
+  componentProps: FullscreenButtonProps,
+  forwardedRef: ForwardedRef<HTMLButtonElement>
+) {
+  const { render, className, style, label, disabled = false, ...elementProps } = componentProps;
+
+  const fullscreen = usePlayer(selectFullscreen);
+
+  const [core] = useState(() => new FullscreenButtonCore());
+  core.setProps({ label, disabled });
+
+  const { getButtonProps, buttonRef } = useButton({
+    displayName: 'FullscreenButton',
+    onActivate: () => core.toggle(fullscreen!),
+    isDisabled: () => disabled || !fullscreen,
+  });
+
+  if (!fullscreen) {
+    logMissingFeature('FullscreenButton', 'fullscreen');
+    return null;
+  }
+
+  return renderElement(
+    'button',
+    { render, className, style },
+    {
+      state: core.getState(fullscreen),
+      ref: [forwardedRef, buttonRef],
+      props: [core.getAttrs(fullscreen), elementProps, getButtonProps()],
+    }
+  );
+});
+
+export namespace FullscreenButton {
+  export type Props = FullscreenButtonProps;
+  export type State = FullscreenButtonCore.State;
+}