After Saul's death, the men of which tribe anointed David as their king?

Answer: Judah

At Hebron the men of Judah anointed David king over Judah, while Saul's son Ish-bosheth reigned over Israel for two years.

“Then the men of Judah came to Hebron, and there they anointed David king over the house of Judah. And they told David, “It was the men of Jabesh-gilead who buried Saul.” Saul’s son Ish-bosheth was forty years old when he began to reign over Israel, and he reigned for two years. The house of Judah, however, followed David.”— 2 Samuel 2:4, 2:10 (BSB)