"Plato's Stepchildren" is the tenth episode of the third season of the American science fiction television series Star Trek. Written by Meyer Dolinsky and directed by David Alexander, it was first broadcast on November 22, 1968.

In the episode, the crew of the Enterprise encounter an ageless and sadistic race of humanoids with the power of telekinesis.

The episode is notable for depicting a kiss between a white man (Kirk) and a black woman (Uhura), which was among the earliest instances of this on a US television show.

It was one of several episodes not screened by the BBC because of their "unpleasant" content, including torture and sadism.

Captain Kirk, along with First Officer Spock and Chief Medical Officer Dr. McCoy, beams down to a planet to investigate a distress call. Once there, they are greeted by a friendly little person named Alexander (Michael Dunn). He leads the landing party to meet the rest of his people, who have adopted classical Greek culture, and named themselves Platonians in honor of the Greek philosopher Plato.

All of the Platonians, except for Alexander, possess telekinetic powers, and the planet's ruling class have become exceedingly arrogant as a result, believing they can do as they please because of their powers. The Platonians explain they "lured" the Enterprise to their planet because their leader, Parmen, requires medical help. After being treated by Dr. McCoy, Parmen demands McCoy remain on the planet to treat other Platonians. When Captain Kirk objects, the Platonians use their powers to punish him.

Alexander tries to tell Kirk and Spock that Parmen wishes to kill them but is afraid.

Parmen repeatedly humiliates Kirk and Spock as Dr. McCoy watches, trying to make him agree to stay on the planet. Later, the Platonians use their powers to force two other Enterprise officers to the planet for their entertainment: Communications Officer Lt. Uhura and Nurse Chapel.