"Elaan of Troyius" is the thirteenth episode of the third season of the American science fiction television series Star Trek. Written and directed by John Meredyth Lucas, it was first broadcast on December 20, 1968. In the episode, the Enterprise ferries a spoiled princess whose betrothal is hoped will bring peace to a star system at war. Elaan of Troyius was written and directed by John Meredyth Lucas, the only person in Star Trek production history ever to both write and direct a filmed Star Trek television episode.