diff --git a/src/lib/integrations/youtube/VideoUploadService.ts b/src/lib/integrations/youtube/VideoUploadService.ts
new file mode 100644
index 0000000..8b30ade
--- /dev/null
+++ b/src/lib/integrations/youtube/VideoUploadService.ts
@@ -0,0 +1,194 @@
+// src/lib/integrations/youtube/VideoUploadService.ts
+
+import fs from 'fs'
+import path from 'path'
+
+import { google } from 'googleapis'
+import type { Payload } from 'payload'
+
+interface VideoMetadata {
+  title: string
+  description: string
+  tags: string[]
+  visibility: 'public' | 'unlisted' | 'private'
+  categoryId?: string
+}
+
+interface UploadOptions {
+  mediaId: number
+  metadata: VideoMetadata
+  scheduledPublishAt?: string
+}
+
+interface UploadResult {
+  success: boolean
+  youtubeVideoId?: string
+  youtubeUrl?: string
+  error?: string
+}
+
+/**
+ * Uploads videos to YouTube via the Data API v3.
+ *
+ * Reads video files from the Payload media collection, resolves OAuth credentials
+ * from the social-accounts collection, and calls youtube.videos.insert().
+ */
+export class VideoUploadService {
+  private payload: Payload
+
+  constructor(payload: Payload) {
+    this.payload = payload
+  }
+
+  /**
+   * Upload a video file from the media collection to YouTube.
+   *
+   * When scheduledPublishAt is provided, the video is uploaded as private
+   * with a publishAt timestamp so YouTube publishes it automatically.
+   */
+  async uploadVideo(options: UploadOptions): Promise<UploadResult> {
+    const { mediaId, metadata, scheduledPublishAt } = options
+
+    // 1. Resolve OAuth credentials from social-accounts
+    const credentials = await this.loadCredentials()
+    if (!credentials) {
+      return {
+        success: false,
+        error: 'No active YouTube social account with valid credentials found',
+      }
+    }
+
+    // 2. Load the media document
+    const media = await this.payload.findByID({
+      collection: 'media',
+      id: mediaId,
+      depth: 0,
+    })
+
+    if (!media) {
+      return { success: false, error: `Media with ID ${mediaId} not found` }
+    }
+
+    const filename = media.filename as string | undefined
+    if (!filename) {
+      return {
+        success: false,
+        error: `Media ${mediaId} has no filename`,
+      }
+    }
+
+    // 3. Verify the file exists on disk
+    const filePath = path.join(process.cwd(), 'media', filename)
+    if (!fs.existsSync(filePath)) {
+      return {
+        success: false,
+        error: `File not found on disk: ${filePath}`,
+      }
+    }
+
+    // 4. Build the OAuth2 client
+    const oauth2Client = new google.auth.OAuth2(
+      process.env.GOOGLE_CLIENT_ID,
+      process.env.GOOGLE_CLIENT_SECRET,
+    )
+    oauth2Client.setCredentials({
+      access_token: credentials.accessToken,
+      refresh_token: credentials.refreshToken,
+    })
+
+    const youtube = google.youtube({ version: 'v3', auth: oauth2Client })
+
+    // 5. Determine privacy status and optional scheduled publish time
+    let privacyStatus: string = metadata.visibility
+    let publishAt: string | undefined
+
+    if (scheduledPublishAt) {
+      privacyStatus = 'private'
+      publishAt = scheduledPublishAt
+    }
+
+    // 6. Execute the upload
+    try {
+      const response = await youtube.videos.insert({
+        part: ['snippet', 'status'],
+        requestBody: {
+          snippet: {
+            title: metadata.title,
+            description: metadata.description,
+            tags: metadata.tags,
+            categoryId: metadata.categoryId,
+          },
+          status: {
+            privacyStatus,
+            ...(publishAt ? { publishAt } : {}),
+          },
+        },
+        media: {
+          body: fs.createReadStream(filePath),
+        },
+      })
+
+      const videoId = response.data.id
+      if (!videoId) {
+        return {
+          success: false,
+          error: 'YouTube API returned no video ID',
+        }
+      }
+
+      return {
+        success: true,
+        youtubeVideoId: videoId,
+        youtubeUrl: `https://www.youtube.com/watch?v=${videoId}`,
+      }
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error)
+      return { success: false, error: `YouTube upload failed: ${message}` }
+    }
+  }
+
+  /**
+   * Find the first active YouTube social account with valid credentials.
+   */
+  private async loadCredentials(): Promise<{
+    accessToken: string
+    refreshToken: string
+  } | null> {
+    const platforms = await this.payload.find({
+      collection: 'social-platforms',
+      where: { slug: { equals: 'youtube' } },
+      limit: 1,
+      depth: 0,
+    })
+
+    const platformId = platforms.docs[0]?.id
+    if (!platformId) return null
+
+    const accounts = await this.payload.find({
+      collection: 'social-accounts',
+      where: {
+        platform: { equals: platformId },
+        isActive: { equals: true },
+      },
+      limit: 1,
+      depth: 0,
+    })
+
+    const account = accounts.docs[0]
+    if (!account) return null
+
+    const creds = account.credentials as {
+      accessToken?: string
+      refreshToken?: string
+    } | undefined
+
+    if (!creds?.accessToken || !creds?.refreshToken) return null
+
+    return {
+      accessToken: creds.accessToken,
+      refreshToken: creds.refreshToken,
+    }
+  }
+}
+
+export type { VideoMetadata, UploadOptions, UploadResult }
diff --git a/tests/unit/youtube/video-upload-service.unit.spec.ts b/tests/unit/youtube/video-upload-service.unit.spec.ts
new file mode 100644
index 0000000..98dfe7d
--- /dev/null
+++ b/tests/unit/youtube/video-upload-service.unit.spec.ts
@@ -0,0 +1,418 @@
+/**
+ * VideoUploadService Unit Tests
+ *
+ * Tests the service that uploads videos to YouTube via the Data API v3.
+ * Validates credential resolution, media file handling, and YouTube API interaction.
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+
+// --- Mocks ---
+
+const mockVideosInsert = vi.fn()
+
+vi.mock('googleapis', () => {
+  class MockOAuth2 {
+    setCredentials(): void {
+      // no-op
+    }
+  }
+
+  return {
+    google: {
+      auth: {
+        OAuth2: MockOAuth2,
+      },
+      youtube: () => ({
+        videos: {
+          insert: mockVideosInsert,
+        },
+      }),
+    },
+  }
+})
+
+const mockExistsSync = vi.fn()
+const mockCreateReadStream = vi.fn()
+
+vi.mock('fs', () => ({
+  default: {
+    existsSync: (...args: unknown[]) => mockExistsSync(...args),
+    createReadStream: (...args: unknown[]) => mockCreateReadStream(...args),
+  },
+  existsSync: (...args: unknown[]) => mockExistsSync(...args),
+  createReadStream: (...args: unknown[]) => mockCreateReadStream(...args),
+}))
+
+const mockFindByID = vi.fn()
+const mockFind = vi.fn()
+
+const mockPayload = {
+  findByID: mockFindByID,
+  find: mockFind,
+} as unknown as import('payload').Payload
+
+// --- Helpers ---
+
+function setupYouTubePlatform(): void {
+  mockFind.mockResolvedValueOnce({
+    docs: [{ id: 100, slug: 'youtube' }],
+    totalDocs: 1,
+  })
+}
+
+function setupSocialAccount(overrides?: Record<string, unknown>): void {
+  mockFind.mockResolvedValueOnce({
+    docs: [
+      {
+        id: 10,
+        isActive: true,
+        credentials: {
+          accessToken: 'yt-access-token',
+          refreshToken: 'yt-refresh-token',
+        },
+        ...overrides,
+      },
+    ],
+    totalDocs: 1,
+  })
+}
+
+function setupMedia(overrides?: Record<string, unknown>): void {
+  mockFindByID.mockResolvedValueOnce({
+    id: 1,
+    filename: 'test-video.mp4',
+    mimeType: 'video/mp4',
+    ...overrides,
+  })
+}
+
+const defaultMetadata = {
+  title: 'My Test Video',
+  description: 'A great video about testing',
+  tags: ['test', 'video'],
+  visibility: 'public' as const,
+  categoryId: '22',
+}
+
+// --- Tests ---
+
+describe('VideoUploadService', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    process.env.GOOGLE_CLIENT_ID = 'test-client-id'
+    process.env.GOOGLE_CLIENT_SECRET = 'test-client-secret'
+  })
+
+  it('should upload a video and return the YouTube video ID', async () => {
+    setupYouTubePlatform()
+    setupSocialAccount()
+    setupMedia()
+    mockExistsSync.mockReturnValue(true)
+    mockCreateReadStream.mockReturnValue('fake-stream')
+
+    mockVideosInsert.mockResolvedValueOnce({
+      data: { id: 'yt-abc123' },
+    })
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const result = await service.uploadVideo({
+      mediaId: 1,
+      metadata: defaultMetadata,
+    })
+
+    expect(result.success).toBe(true)
+    expect(result.youtubeVideoId).toBe('yt-abc123')
+    expect(result.youtubeUrl).toBe('https://www.youtube.com/watch?v=yt-abc123')
+    expect(result.error).toBeUndefined()
+
+    expect(mockVideosInsert).toHaveBeenCalledWith(
+      expect.objectContaining({
+        part: ['snippet', 'status'],
+        requestBody: expect.objectContaining({
+          snippet: {
+            title: 'My Test Video',
+            description: 'A great video about testing',
+            tags: ['test', 'video'],
+            categoryId: '22',
+          },
+          status: {
+            privacyStatus: 'public',
+          },
+        }),
+        media: { body: 'fake-stream' },
+      }),
+    )
+  })
+
+  it('should set privacyStatus to private and include publishAt for scheduled uploads', async () => {
+    setupYouTubePlatform()
+    setupSocialAccount()
+    setupMedia()
+    mockExistsSync.mockReturnValue(true)
+    mockCreateReadStream.mockReturnValue('fake-stream')
+
+    mockVideosInsert.mockResolvedValueOnce({
+      data: { id: 'yt-scheduled-1' },
+    })
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const result = await service.uploadVideo({
+      mediaId: 1,
+      metadata: { ...defaultMetadata, visibility: 'public' },
+      scheduledPublishAt: '2026-03-01T12:00:00Z',
+    })
+
+    expect(result.success).toBe(true)
+    expect(result.youtubeVideoId).toBe('yt-scheduled-1')
+
+    expect(mockVideosInsert).toHaveBeenCalledWith(
+      expect.objectContaining({
+        requestBody: expect.objectContaining({
+          status: {
+            privacyStatus: 'private',
+            publishAt: '2026-03-01T12:00:00Z',
+          },
+        }),
+      }),
+    )
+  })
+
+  it('should return error when no YouTube social account exists', async () => {
+    // Platform found, but no account
+    setupYouTubePlatform()
+    mockFind.mockResolvedValueOnce({ docs: [], totalDocs: 0 })
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const result = await service.uploadVideo({
+      mediaId: 1,
+      metadata: defaultMetadata,
+    })
+
+    expect(result.success).toBe(false)
+    expect(result.error).toContain('No active YouTube social account')
+    expect(mockFindByID).not.toHaveBeenCalled()
+  })
+
+  it('should return error when social account has no credentials', async () => {
+    setupYouTubePlatform()
+    setupSocialAccount({ credentials: {} })
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const result = await service.uploadVideo({
+      mediaId: 1,
+      metadata: defaultMetadata,
+    })
+
+    expect(result.success).toBe(false)
+    expect(result.error).toContain('No active YouTube social account')
+    expect(mockFindByID).not.toHaveBeenCalled()
+  })
+
+  it('should return error when YouTube platform is not found', async () => {
+    mockFind.mockResolvedValueOnce({ docs: [], totalDocs: 0 })
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const result = await service.uploadVideo({
+      mediaId: 1,
+      metadata: defaultMetadata,
+    })
+
+    expect(result.success).toBe(false)
+    expect(result.error).toContain('No active YouTube social account')
+  })
+
+  it('should return error when media document is not found', async () => {
+    setupYouTubePlatform()
+    setupSocialAccount()
+    mockFindByID.mockResolvedValueOnce(null)
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const result = await service.uploadVideo({
+      mediaId: 999,
+      metadata: defaultMetadata,
+    })
+
+    expect(result.success).toBe(false)
+    expect(result.error).toContain('Media with ID 999 not found')
+  })
+
+  it('should return error when media has no filename', async () => {
+    setupYouTubePlatform()
+    setupSocialAccount()
+    setupMedia({ filename: undefined })
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const result = await service.uploadVideo({
+      mediaId: 1,
+      metadata: defaultMetadata,
+    })
+
+    expect(result.success).toBe(false)
+    expect(result.error).toContain('has no filename')
+  })
+
+  it('should return error when file does not exist on disk', async () => {
+    setupYouTubePlatform()
+    setupSocialAccount()
+    setupMedia()
+    mockExistsSync.mockReturnValue(false)
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const result = await service.uploadVideo({
+      mediaId: 1,
+      metadata: defaultMetadata,
+    })
+
+    expect(result.success).toBe(false)
+    expect(result.error).toContain('File not found on disk')
+    expect(result.error).toContain('test-video.mp4')
+  })
+
+  it('should return error when YouTube API returns no video ID', async () => {
+    setupYouTubePlatform()
+    setupSocialAccount()
+    setupMedia()
+    mockExistsSync.mockReturnValue(true)
+    mockCreateReadStream.mockReturnValue('fake-stream')
+
+    mockVideosInsert.mockResolvedValueOnce({
+      data: { id: null },
+    })
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const result = await service.uploadVideo({
+      mediaId: 1,
+      metadata: defaultMetadata,
+    })
+
+    expect(result.success).toBe(false)
+    expect(result.error).toContain('YouTube API returned no video ID')
+  })
+
+  it('should return error when YouTube API throws', async () => {
+    setupYouTubePlatform()
+    setupSocialAccount()
+    setupMedia()
+    mockExistsSync.mockReturnValue(true)
+    mockCreateReadStream.mockReturnValue('fake-stream')
+
+    mockVideosInsert.mockRejectedValueOnce(new Error('quotaExceeded'))
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const result = await service.uploadVideo({
+      mediaId: 1,
+      metadata: defaultMetadata,
+    })
+
+    expect(result.success).toBe(false)
+    expect(result.error).toContain('YouTube upload failed')
+    expect(result.error).toContain('quotaExceeded')
+  })
+
+  it('should support unlisted visibility', async () => {
+    setupYouTubePlatform()
+    setupSocialAccount()
+    setupMedia()
+    mockExistsSync.mockReturnValue(true)
+    mockCreateReadStream.mockReturnValue('fake-stream')
+
+    mockVideosInsert.mockResolvedValueOnce({
+      data: { id: 'yt-unlisted-1' },
+    })
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const result = await service.uploadVideo({
+      mediaId: 1,
+      metadata: { ...defaultMetadata, visibility: 'unlisted' },
+    })
+
+    expect(result.success).toBe(true)
+    expect(mockVideosInsert).toHaveBeenCalledWith(
+      expect.objectContaining({
+        requestBody: expect.objectContaining({
+          status: { privacyStatus: 'unlisted' },
+        }),
+      }),
+    )
+  })
+
+  it('should omit categoryId from snippet when not provided', async () => {
+    setupYouTubePlatform()
+    setupSocialAccount()
+    setupMedia()
+    mockExistsSync.mockReturnValue(true)
+    mockCreateReadStream.mockReturnValue('fake-stream')
+
+    mockVideosInsert.mockResolvedValueOnce({
+      data: { id: 'yt-nocat-1' },
+    })
+
+    const { VideoUploadService } = await import(
+      '@/lib/integrations/youtube/VideoUploadService'
+    )
+
+    const service = new VideoUploadService(mockPayload)
+    const { categoryId: _, ...metadataWithoutCategory } = defaultMetadata
+    const result = await service.uploadVideo({
+      mediaId: 1,
+      metadata: metadataWithoutCategory,
+    })
+
+    expect(result.success).toBe(true)
+    expect(mockVideosInsert).toHaveBeenCalledWith(
+      expect.objectContaining({
+        requestBody: expect.objectContaining({
+          snippet: expect.objectContaining({
+            title: 'My Test Video',
+            categoryId: undefined,
+          }),
+        }),
+      }),
+    )
+  })
+})