"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 This episode was withdrawn by the BBC in the UK because of 'sadistic plot elements' during the initial run in 1971 and was not shown until a repeat run in January 1994.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, used by the Federation to house the criminally insane due to its poisonous surface conditions. They carry a shipment of medicine to be used to cure the patients.

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 not who they think he is. Too late, they discover the real Cory imprisoned in a cell, and their host introduces himself as Garth of Izar (Steve Ihnat). Garth is a former starship captain who became injured and mentally unstable after a rescue mission; he physically recovered with help from the people of Antos that taught him the ability to shapeshift to heal his own injuries and take the form of others. When Garth threatened to attack Antos, his crew mutinied and stranded him. Kirk looked up to Garth as one of his personal heroes as a cadet at Starfleet Academy and still respects him despite his fall from grace.

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