A startup movie is an undocumented feature in QuickTime for the Classic Mac OS. It is triggered whenever a movie, renamed as Startup Movie, is put loose in the System Folder.

The startup movie launches as soon as the icon for the QuickTime extension is shown during the startup process. It finishes, and remains, on the last frame until the Macintosh has completed startup.

In earlier versions of the Macintosh system software, the movie would play with its soundtrack intact. However, beginning with later versions, only the video was supported. On some versions of the Mac OS, applying such a trick could crash the Mac!