Joab (lit, "Jehovah is his father") was the nephew of King David, the son of Zeruiah in the Bible. He was made the captain of David's army (2 Samuel 8:16; 20:23; 1 Chronicles 11:6; 18:15; 27:34). He had two brothers, Abishai and Asahel. Asahel was killed by Abner, for which Joab took revenge by treacherously murdering Abner (2 Samuel 2:13-32; 3:27). After leading the assault on the fortress of Mount Zion, he was promoted to the rank of General (1 Chronicles 27:34). He led the army against Syria, Ammon, and Edom. He took part in David's murder of Uriah (2 Samuel 11:14-25) and later pursued and killed Absalom (2 Samuel 18:1-33).

However, even with all that Joab had done for David, David replaced him as commander of the army with his cousin, Amasa (2 Samuel 17:25; 19:13). Joab later killed Amasa (2 Samuel 20:8-13; 1 Kings 2:5).

After David's death Joab supported the claim of Adonijah for the throne over that of Solomon (1 Kings 1:7; 2:28), and for this Solomon ordered his death by the hand of Benaiah (1 Kings 2:29-34), who then replaced him as commander of the army. Joab was buried in 'the wilderness' (1 Kings 2:34).