Alcmaeon of Croton (/ælkˈmiːɒn/; Greek: Ἀλκμαίων ὁ Κροτωνιάτης, Alkmaiōn, gen.: Ἀλκμαίωνος; fl. 5th century BC) was an early Greek medical writer and philosopher-scientist. He has been described as one of the most eminent natural philosophers and medical theorists of antiquity and he has also been referred to as "a thinker of considerable originality and one of the greatest philosophers, naturalists, and neuroscientists of all time." His work in biology has been described as remarkable, and his originality made him likely a pioneer. Because of difficulties dating Alcmaeon's birth, his importance has been neglected.