2 Kings 21:19 (ESV)

19 Amon was twenty-two years old when he began to reign, and he reigned two years in Jerusalem. His mother’s name was Meshullemeth the daughter of Haruz of Jotbah.

See also 2 Chronicles 33:21–25. 2 Kings 21:19 merely mentions the start of Amon’s reign, the son of Manasseh, with further information about his mother and her origin.