Updated: October 11, 2023

Lost in Space is an American science fiction television series, following the adventures of a family of pioneering space colonists whose ship goes off course. It was created and produced by Irwin Allen, filmed by 20th Century Fox Television, and broadcast on CBS. The show ran for three seasons, with 83 episodes airing between September 15, 1965, and March 6, 1968. The first television season was filmed in black and white, with the second and third seasons filmed in color.

Though the original television series concept centered on the Robinson family, many later story lines focused primarily on Dr. Zachary Smith, played by Jonathan Harris. Smith, along with the Robot, was absent from the pilot as the addition of their characters was decided once the series had been commissioned for production. Originally written as an utterly evil but careless saboteur, Smith gradually becomes the troublesome, self-centered, incompetent foil who provides the comic relief for the show and causes most of the episodic conflict and misadventures. In the unaired pilot, what causes the group to become lost in space is a chance encounter with a meteor storm, but in the first aired episode, it is Smith's sabotage and unplanned presence on the ship that sets the ship off course into the meteor field. Smith is thus the key to the story.