Athenian family important in the 6th–5th century BC.
During the archonship (magistracy) of the Alcmaeonid Megacles (632? BC), the family was banished for murder; it returned twice to oust the tyrant Peisistratus before again being exiled. Megacles' son Marathon (490). {{link=Alcibiades">Alcibiades and Pericles were both Alcmaeonids.