Beta II was a Class M planet, the second of the Beta system. It had at least one native lifeform, the Betasaur.

In 2266, the USS Enterprise detected large deposits of valuable ores on Beta II and a landing party was sent down on a surveying expedition. In fact, the mineral deposits had been faked by Klingons to lure the Enterprise there and replace Captain James T. Kirk with a duplicate. The Enterprise left the Beta II after being ordered to escort Omegan ambassador T'Ki home, but returned in pursuit of the duplicate Kirk, who had fled after the crew mutinied against him. Back on Beta II, Spock exposed the Klingon plot and rescued the real Kirk. (TOS comic: "The Enterprise Mutiny")

Beta II orbited a red giant. It had a high mineral content and became a Federation colony with mining as its primary function.

According to a Starfleet Academy simulator scenario, two years after its founding, a radioactive object approaching the planet was averted by the USS Banting. (TOS video game: Starfleet Academy Starship Bridge Simulator)