(Ἄφίδνος; Aphídnos). Autochthonous, eponymous king of the Attic town of Aphidna (Steph. Byz. s. v. Aphidna). He was entrusted by Theseus with the task of guarding Aithra, Theseus' mother and also the abducted Helen (Plut. Thes. 31; 33). During the attack on Aphidna by the Dioscuri (heavenly twins), he wounded Castor in the right thigh (Polemon fr. 10). A. adopted the Dioscuri and initiated them into the Eleusinian Mysteries (Plut. Thes. 33,2).