A sound editor is a creative professional responsible for selecting and assembling sound recordings in preparation for the final sound mixing or mastering of a television program, motion picture, video game, or any production involving recorded or synthetic sound. The sound editor works with the supervising sound editor. The supervising sound editor often assigns scenes and reels the sound editor based on the editor's strengths and area of expertise. Sound editing developed out of the need to fix the incomplete, undramatic, or technically inferior sound recordings of early talkies, and over the decades has become a respected filmmaking craft, with sound editors implementing the aesthetic goals of motion picture sound design.

The Academy of Motion Picture Arts and Sciences recognizes the artistic contribution of exceptional sound editing with the Academy Award for Best Sound Editing.

There are primarily three divisions of sound that are combined to create a final mix, these being dialogue, effects, and music. In larger markets such as New York and Los Angeles, sound editors often specialize in only one of these areas, thus a show will have separate dialogue, effects, and music editors. In smaller markets, sound editors are expected to know how to handle it all, often crossing over into the mixing realm as well. Editing effects is likened to creating the sonic world from scratch, while dialogue editing is likened to taking the existing sonic world and fixing it. Dialogue editing is more accurately thought of as "production sound editing", where the editor takes the original sound recorded on the set, and using a variety of techniques, makes the dialogue more understandable, as well as smoother, so the listener doesn't hear the transitions from shot to shot (often the background sounds underneath the words change dramatically from take to take). Among the challenges that effects editors face are creatively adding together various elements to create believable sounds for everything you see on screen, as well as memorizing their sound effects library.