Clepsysaurus (from Greek: κλεψύδρα klepsúdra, 'water thief' and Greek: σαῦρος saûros, 'lizard') is a dubious[1] genus of extinct archosaur from the Carnian[2] Passaic Formation and Lockatong Formation of Lehigh County, and York County, Pennsylvania.

[4] The holotype of C. pennsylvanicus, ANSP 9526, 9555-71, 9594-5, consists of teeth, ribs and vertebrae from the Passaic Formation of Pennsylvania.

[3] Other specimens of C. pennsylvanicus are known, including ANSP 15071 (a left anterior dentary with 23 teeth, a right dentary with 30 teeth and a portion of the right temporal region), AMNH 2337 (a single tooth) and ANSP 15529 (18 large blocks of matrix containing bone material, comprising postcranial and rib fragments alongside 12 small bone fragments comprising vertebral and rib fragments, one isolated vertebral centrum, broken in half laterally and glued together, and 40 small bone fragments, some of them being rib fragments).

[7] The holotype of C. veatleianus, AMNH 2331, consists of a single broken tooth, with AMNH 2330, a tooth, as a referred specimen—these were found in the Phoenixville tunnel in York County, Pennsylvania.

[4] Clepsysaurus was traditionally classed as a sauropodomorph,[4][5] but more recent studies indicate that it was either a dubious basal archosaur[8] or a member of the Phytosauria.