Which king of Judah married Ahab's daughter?

Answer: Jehoram

Jehoram son of Jehoshaphat, king of Judah, walked in the ways of Ahab's house, for he married a daughter of Ahab.

“In the fifth year of the reign of Joram son of Ahab over Israel, Jehoram son of Jehoshaphat succeeded his father as king of Judah.”— 2 Kings 8:16 (BSB)