Achaeans, people of ancient Greece, of unknown origin. In Homer, the Achaeans are specifically a Greek-speaking people of S Thessaly. Historically, they seem to have appeared in the Peloponnesus during the 14th and 13th cent. BC, and c.1250 BC they became the ruling class. There is no sharp line of separation between the earlier Mycenaean civilization and the Achaean; the cultures seem to have intermingled. The invasions of the Dorians supposedly forced some of the Achaeans out to Asia Minor; others were concentrated in the region known in classical times as Achaea.