"Who Mourns for Adonais?" is episode No. 31, production No. 33, of the second season of the original science fiction television series, Star Trek. Written by Gilbert Ralston and Gene L. Coon, and directed by Marc Daniels, it was first broadcast September 22, 1967, and repeated May 10, 1968. The allusion is to the 1821 elegy Adonais by Percy Bysshe Shelley.

In this episode, the crew of the Enterprise are held captive by an alien who claims to be the Greek god Apollo.

A huge energy field in the shape of a glowing green hand appears and grabs the Enterprise, halting its movement. Captain James T. Kirk tries to wriggle the ship free, but to no avail. A humanoid apparition appears on the bridge viewscreen and addresses the ship's crew. Kirk demands that the ship be set free, but the being responds by tightening the grip, threatening to crush the ship.

Kirk leads a landing party that includes Lieutenant Carolyn Palamas. The team arrives in what appears to be an ancient garden from Mount Olympus, where they encounter the humanoid who identifies himself as the god Apollo. He informs the party that he will not allow them to leave, and renders the team's communicators and transporter room nonfunctional. He indicates that he wants the crew of the Enterprise to serve and worship him as their god. Kirk defiantly refuses.

Apollo's attention shifts toward Carolyn, angering Mr. Scott, who steps forward to defend her against Apollo's advances. Apollo destroys his weapon and announces he will take Carolyn as his consort. After displaying his power, Apollo appears drained and retires with Carolyn to another area of the planet.

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