Josiah was the son of Amon and fifteenth king of Judah. Josiah descending from the loins of Amon seems every bit as improbable as Manasseh descending from the loins of Hezekiah, because Josiah was exceedingly righteous.
Josiah ascended the throne when he was only eight years old and though it took him a while to get started on the road to righteousness, once he got started there was no stopping him. He tore down the altars of Baal, smashed the Asherah poles, purified and repaired the temple, and removed all the idols from the land over which he reigned.
While repairing the temple, Hilkiah the high priest discovered a roll which was probably the original copy of the law, the entire Pentateuch, written by Moses. When this book was read to him, the king sent for Huldah, the "prophetess," for her counsel. She spoke to him words of encouragement, telling him that he would be gathered to his fathers in peace before the threatened days of judgment came. Josiah immediately gathered the people together, and engaged them in a renewal of their ancient national covenant with God, celebrating the Passover, something not done in Israel since the time of Hezekiah.
Soon thereafter, Pharaoh Neco king of Egypt went up to fight the Assyrians, and Josiah marched out to meet him in battle.
But Neco sent messengers to him, saying, "What quarrel is there between you and me, O king of Judah? It is not you I am attacking at this time, but the house with which I am at war. God has told me to hurry; so stop opposing God, who is with me, or he will destroy you."
(2 Chronicles 35:21)
Josiah, however, instead of turning away, disguised himself and engaged Neco in battle. It proved to be a fatal error as he was wounded by a random arrow. His attendants took him off the field to Jerusalem but he died on the way. He had reigned for 38 years.
He was buried with the greatest honours in fulfilment of Huldah's prophecy and the prophet Jeremiah composed a funeral elegy on this the best of the kings of Israel.