The USS Regulus (NCC-1840) was a Constitution-class (Tikopai-subclass) Federation heavy cruiser starship ordered for Starfleet service in the 23rd century, named for the star system at Regulus.
Construction of Regulus was authorized by the Starfleet appropriation of stardate 5930. (TOS reference: Star Fleet Technical Manual)
In 2269, the Regulus was assigned to survey the Antares Rift, but took damage and had to abandon her mission. (TOS video game: Judgment Rites)
Ulysses Montaya served aboard this vessel at some point in his career. (TOS video game: Judgment Rites)