Abiathar, in the Old Testament, son of Ahimelech, priest of Nob. He was the sole survivor of a massacre carried out by Doeg. Fleeing to David, he remained with him throughout his wanderings and his reign. He was loyal through the rebellion of Absalom, but he supported Adonijah against Solomon. Abiathar probably represents an early rival house to that of Zadok, the official priestly family of Jerusalem down to the Exile (1 Samuel 22:20–23; 2 Samuel 15:24–37; and 1 Kings 2:26–27).