Alduin, Auduin, or Audoin was king of the Lombards from 539 or 546 to 563 or 565. The Lombards became, under him, a fœderatus of the Byzantines (541), signing a treaty with Justinian I which gave them power in Pannonia and the north. Beginning in 551, he was obliged to send troops to serve Narses in Italy against the Ostrogoths.