Corinthia VII was a planet, the seventh planet of the Corinthia star system, located somewhere in the galaxy's Alpha or Beta Quadrants.
History and specifics
Corinthia VII was a class M planet visited by the Federation starship USS Enterprise sometime after the year 2254. Though initially believed to be devoid of any advanced lifeforms, a landing party discovered huge subterranean creatures on the planet, one of which killed landing party member Ensign Williams. (TOS - Strange New Worlds I short story: "A Private Anecdote")