Spock, commonly Mister Spock, is a fictional character in Star Trek, first portrayed by Leonard Nimoy. Spock serves aboard the starship Enterprise, as science officer and first officer, and later as commanding officer of two iterations of the vessel. Spock's mixed human-Vulcan heritage serves as an important plot element in many of the character's appearances. Along with Captain James T. Kirk and Dr. Leonard "Bones" McCoy, he is one of the three central characters in the original Star Trek series and its films.

After retiring from Starfleet, Spock serves as a Federation ambassador, contributing toward the détente between the Federation and the Klingon Empire. In his later years, he serves as Federation ambassador to the Romulan Empire and becomes involved in the ill-fated attempt to save Romulus from a supernova.