Achaeus is a masculine given name. It may refer to:
People Achaeus of Eretria (born 484 BC), tragic poet Achaeus of Syracuse (4th century BC), tragic poet Achaeus (son of Seleucus I Nicator) (3rd century BC), Greek Macedonian nobleman Achaeus (general) (died 213 BC), ruler of part of the Greek Seleucid kingdom
Mythological figures Achaeus (mythology), three figures in Greek mythology
See also Achaius, one of the legendary kings of Scotland