Manasseh (; Hebrew: מְנַשֶּׁה‎ Mənaššé, "Forgetter"; Akkadian: 𒈨𒈾𒋛𒄿 Menasî [me-na-si-i]; Greek: Μανασσῆς Manasses; Latin: Manasses) was the fourteenth king of the Kingdom of Judah. He was the oldest of the sons of Hezekiah and his mother Hephzibah (2 Kings 21:1). He became king at the age of 12 and reigned for 55 years (2 Kings 21:1; 2 Chronicles 33:1).

The biblical account of Manasseh is found in 2 Kings 21:1–18 and 2 Chronicles 32:33–33:20. He is also mentioned in Jeremiah 15:4, where the prophet Jeremiah predicts "four forms of destruction" for the people of Judah because of the evil done by Manasseh in Judah.

Manasseh was the first king of Judah who was not contemporary with the northern kingdom of Israel, which had been destroyed by the Assyrians in c. 720 BC, with much of its population deported. He re-instituted polytheistic worship and reversed the religious changes made by his father Hezekiah, for which he is condemned by several biblical verses.

He was married to Meshullemeth, daughter of Haruz of Jotbah, and they had a son Amon, who succeeded him as king of Judah upon his death. Hezekiah, Manasseh and Amon are mentioned in the genealogy of Jesus in Matthew's gospel.

After a reign of 55 years, the longest in the history of Judah, he died in c. 643 BC and was buried in the garden of Uzza, the "garden of his own house" (2 Kings 21:17–18; 2 Chronicles 33:20), and not in the City of David, among his ancestors. The biblical narratives both report Manasseh's accession to the throne at the time of his father's death. However, Edwin Thiele concluded he had commenced his reign as co-regent with his father Hezekiah in 697/696 BC, with the co-regency lasting 12 years and his sole reign beginning in 687/686 BC and continuing until his death in 643/642 BC.