Archidamus I, also spelled Archidamos I (Ancient Greek: Ἀρχίδαμος Α΄), was a king of Sparta, 12th of the Eurypontids. He reigned from c. 660 to c. 645.
His relationship to other Spartan kings is unclear. According to Herodotus, Archidamus was the son of Anaxandridas I and fathered Anaxilas. According to Pausanias, Archidamus was the son of Anaxidamus and fathered Agasicles.