Orthoo was a planet located somewhere in the space of the galaxy's Alpha or Beta Quadrant. It was the homeworld of the Orthoo civilization.
History and specifics
In 2265, the Federation starship USS Enterprise visited Orthoo. During their visit, Captain James T. Kirk provided King Yo with security guards to protect the Great Eye of Ara, a holy relic. The giant ruby disappeared during their watch, and Montgomery Scott described the incident as almost costing them their necks. (TOS comic: "Furlough to Fury")