"That Which Survives" is the seventeenth episode of the third season of the American science fiction television series Star Trek. Written by John Meredyth Lucas (based on a story by D.C. Fontana under the pseudonym Michael Richards) and directed by Herb Wallerstein, it was first broadcast January 24, 1969.
In the episode, the crew of the Enterprise visit an abandoned planet guarded by a mysterious woman.