USS Sphinx was a Centaurus-class starship in service to Starfleet in the mid 23rd century. As of 2268, it was commanded by Captain Jack Casden. That year, the Sphinx transported a number of scientists from Deep Space Station R-5 to a secret base in the Lantaru sector. When Captain Casden learned the illegal nature of the research being conducted at the station and threatened to reveal it, he and the Sphinx crew were murdered, and the Sphinx nearly destroyed. The hulk was recovered by the USS Enterprise and towed to Deep Space Station M-20 for investigation. (TOS - Section 31 novel: Cloak)