Updated: June 29, 2024

The theme music for the opening and closing credits was written by John Williams, who was listed in the credits as "Johnny Williams."

The original pilot and much of season one reused Bernard Herrmann's eerie score from the 1951 classic "The Day the Earth Stood Still."

For season three, the opening theme was revised ( again by Williams ) to a more exciting and faster tempo score, accompanied by live action shots of the cast, featuring a pumped-up countdown from seven to one to launch each week's episode. Seasons 1 and 2 had animated figures "life-roped" together drifting "hopelessly Lost in Space" and set to a dizzy and comical score.

Much of the incidental music in the series was written by Williams ( who scored four episodes ) and other notable film and television composers including Alexander Courage ( composer of the Star Trek theme ) who contributed six scores to the series. His most recognizable ( "Wild Adventure" ) included his key theme for "Lorelei" composed for organ, woodwinds, and harp thus cementing this highly recognizable theme with Williams' own "Chariot" and main theme for the series.

A series of soundtrack CDs were released containing only background and incidental music from the original TV series.