How long did Amon reign?

Answer: Two years

Amon was twenty-two years old when he became king, and he reigned two years.

“Amon was twenty-two years old when he became king, and he reigned in Jerusalem two years. His mother’s name was Meshullemeth daughter of Haruz; she was from Jotbah.”— 2 Kings 21:19 (BSB)