Omicron Theta IV was a planet, the fourth planet of the Omicron Theta system, located in or near Federation space in the galaxy's Alpha or Beta Quadrant.
History and specifics
As long as two thousand years ago, the world was an inhabited member of the system-wide Tarachi Empire. The Second Great War between the Chitik and Tarachi led to the detonation of nuclear weapons across the surface of the planet, leaving it lifeless and heavily cratered, with massive lakes of molten glass.
In 2277, the USS Enterprise visited the system. After having scanned the planet, Spock determined that Omicron Theta V would be a better candidate to send a landing party. (TOS - Star Trek II Short Stories short story: "The Secret Empire")