Selemnus was a handsome youth who loved the sea-nymph Argyra. She tired of him, and when he died of heartbreak, Aphrodite changed him into the river Selemnus. If his name derives from selas, 'bright' (as for Selene), then it closely approximates the origin of Argyra's own name (which see). The story seems to have originated from a spring called Argyra that was located near the river Selemnus in Achaea.