"Whom Gods Destroy" is a third season episode of the American science fiction television series, Star Trek. It is episode #69, production #71, and was broadcast on January 3, 1969. It was written by Lee Erwin, based on a story by Lee Erwin and Jerry Sohl, and directed by Herb Wallerstein. The title is based on a phrase spoken by Prometheus in Henry Wadsworth Longfellow's poem, "The Masque of Pandora" (1875): "Whom the gods would destroy, they first make mad." This episode was withdrawn by the BBC in the UK because of 'sadistic plot elements' during the initial run in 1971 and was not shown until a repeat run in January 1994. In the episode, Captain Kirk faces off with a demented shape-shifting starship captain determined to control the universe.

On stardate 5718.3, the Federation starship USS Enterprise arrives at the planet Elba II, home to a Federation facility for the criminally insane, carrying a shipment of a new medication.

Captain Kirk and First Officer Spock beam down with the shipment and meet the facility director Donald Cory (Keye Luke). He gives them a brief tour, where one of the inmates, an Orion female named Marta, warns the two that Cory is an imposter. The real Cory is then discovered in a cell, and their host introduces himself as Garth of Izar (Steve Ihnat). Garth is a former starship captain, mentally unstable as the result of an injury, and he has acquired the ability to shapeshift using a method taught to him to heal his own injuries.

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