Jan (Johann) IV of Nassau (1 August 1410, Dillenburg – 3 February 1475, Breda) was Count of Nassau, Dietz and Dillenburg. He was the son of Engelbert I of Nassau, Count of Nassau and Dillenburg, Lord of Breda and Johanna of Polanen. [1]
He married Maria, Countess of Loon and Heinsberg, Lady of Millen, Gangelt and Vucht (born in 1424), the daughter of John VIII of Heinsberg, on 7 February 1440. They had children, including: