Alcmaeon, Alkmaion, Alcmeon, or Alkmaon may refer to:

• Alcmaeon, the great-grandson of Nestor, from whom the Alcmaeonidae claimed descent
• Alcmaeon (mythology), one of the Epigoni
• Alcmaeon in Corinth, a lost play by Euripides
• Alcmaeon in Psophis, a lost play by Euripides
• Alcmaeon (King of Athens), the last king of Athens
• Alcmaeon, son of Megacles, 6th century BC commander during the Cirrhaean War
• Alcmaeon of Croton (mid-fifth century B.C.), an Ancient Greek philosopher and medical theorist