Athenian family important in the 6th5th 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 Cleisthenes became archon in 525/524, but in 514 Peisistratus' son Hippias again exiled the family for murdering his brother. The family reestablished itself after the Spartans drove out the Peisistratids in 510. The next generation may have aided the Persians at the Battle of Marathon (490). Alcibiades and Pericles were both Alcmaeonids.