Achaea () or Achaia (; , Akhaia, ]) was (and is) the northernmost region of the Peloponnese, occupying the coastal strip north of Arcadia. Its approximate boundaries were to the south the mountain range of Erymanthus, to the south-east the range of Cyllene, to the east Sicyon, and to the west the Larissos river. Apart from the plain around Dyme, to the west, Achaea was generally a mountainous region.