Alcmaeon (; , Alkmaiōn, gen.: Ἀλκμαίωνος; 5th century BCE) of Croton (in Magna Graecia) was one of the most eminent natural philosophers and medical theorists of antiquity. His father's name was Peirithus (Peirithos). He is said by some to have been a pupil of Pythagoras, and he is believed to have been born c. 510 BCE. Although he wrote primarily about medical topics, there is some suggestion that he was a philosopher of science, not a physician. He also practiced astrology and meteorology. Nothing more is known of the events of his life.

Alcmaeon (; , Alkmaiōn, gen.: Ἀλκμαίωνος; 5th century BCE) of Croton (in Magna Graecia) was one of the most eminent natural philosophers and medical theorists of antiquity. His father's name was Peirithus (Peirithos). He is said by some to have been a pupil of Pythagoras, and he is believed to have been born c. 510 BCE. Although he wrote primarily about medical topics, there is some suggestion that he was a philosopher of science, not a physician. He also practiced astrology and meteorology. Nothing more is known of the events of his life.