An S3M file is a song module created with Scream Tracker 3 or later. It contains sound samples and a list of notes that make up music patterns. Each note is played back using one of the samples stored in the file.

Scream Tracker was a multi-track audio tracker developed for DOS. While the Scream Tracker program is no longer supported, S3M files are recognized by several different MOD players and other audio playback programs.