(Ἀλκμαίων), son of the Megacles who was guilty of sacrilege with respect to the followers of Cimon, was invited by Croesus to Sardis in consequence of the services he had rendered to an embassy sent by Croesus to consult the Delphic oracle. On his arrival at Sardis, Croesus made him a present of as much gold as he could carry out of the treasury. Alcmaeon took the king at his word, by putting on a most capacious dress, the folds of which (as well as the vacant space of a pair of very wide boots, also provided for the occasion) he stuffed with gold, and then filled his mouth and hair with gold dust. Croesus laughed at the trick, and presented him with as much again (about 590 B. C.). The wealth thus acquired is said to have contributed greatly to the subsequent prosperity of the Alcmaeonidae. (Hdt. 6.125.)

Alclmaeon was a breeder of horses for chariotraces, and on one occasion gained the prize in a chariot-race at Olympia. (Herod. l.c. ; Isocrates, de Bigis, c. 10. p. 351.) We are informed by Plutarch (Plut. Sol. c. 11), that he commanded the Athenians in the Cirrhaean war, which began B. C. 600.