Count 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 van Polanen. 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.