Prosymnus (Ancient Greek: Πρόσυμνος) (also known as Polymnus (Πόλυμνος) and Hypolipnus) was, in Greek mythology, a shepherd living near the reputedly bottomless Alcyonian Lake, hazardous to swimmers, which lay in the Argolid, on the coast of the Gulf of Argos, near the prehistoric site of Lerna.