Psamathus or Psamathous (), called by Strabo Amathus or Amathous (Ἀμαθοῦς), was a harbour of ancient Laconia on the Mani Peninsula. The Periplus of Pseudo-Scylax places it "back-to-back" (ἀντίπυλος) with the harbour of Achilleius.[ Periplus of Pseudo-Scylax 46.]
Pausanias places it near Cape Taenarum (Matapan) and Asine, at about 150 stadia from Teuthrone. He says that at the end of Cape Matapan there was a temple in the shape of a cave and a statue of Poseidon. Strabo and other ancient writers call Psamathus a polis (city-state).
Its site is located near the modern Porto Kagio.