The Class M-3 Model B-9 General Utility Non-Theorizing Environmental Control Robot, known simply as the Robot, is a fictional character in the television series "Lost in Space". His full designation was only occasionally mentioned on the show.

The Robot was performed by Bob May in a prop costume built by Bob Stewart. The voice was primarily dubbed by Dick Tufeld, who was also the series' narrator, and Jorge Arvizu for the Spanish dubbing. The Robot was designed by Robert Kinoshita, who also designed "Forbidden Planet's Robby the Robot". Both robots appear together in "Lost in Space" episode #20, "War of the Robots", and in episode #60, "Condemned of Space".

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