133 Cyrene is a fairly large and very bright main-belt asteroid that was discovered by J. C. Watson on August 16, 1873, and named after Cyrene, a nymph, daughter of king Hypseus and beloved of Apollo in Greek mythology. It is classified as an S-type asteroid based upon its spectrum. It is listed as a member of the Hecuba group of asteroids that orbit near the 2:1 mean-motion resonance with Jupiter.In the Tholen classification system, it is categorized as a stony SR-type asteroid.