Delta III was a planet located in the galaxy's Alpha or Beta Quadrants, the third planet in the Delta Triciatu star system, in Federation space. By the 23rd century Delta III's inhabitants had began to colonize the Vega system. (ST reference: The Worlds of the Federation)

The planet was famous for its palaces, though Spock felt they were surpassed by the City of a Thousand Lights. (TOS comic: "Dark Traveler")