A distant Federation colony world, the next stop on the Karidian Company's tour in The Conscience of the King and the place where Janice Lester planned to abandon Kirk in Turnabout Intruder.
Benecia is a Federation colony mentioned in two Original Series episodes. In The Conscience of the King it is the next engagement of the Karidian Company of Players, and Kirk arranges for the Enterprise to carry the actors there so that he can study Anton Karidian, whom he suspects of being Kodos the Executioner.
In Turnabout Intruder the colony matters again. Janice Lester, occupying Kirk's body, orders the ship off its course for Starbase 2 and towards the Benecia colony, intending to leave the real Kirk, trapped in her body, in its care. Spock and McCoy object that the colony's medical facilities are far too primitive for a patient in that condition, and the strange order helps to convince the senior officers that their captain is not himself.