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 of Loon-Heinsberg, Lady of Millen, Gangelt and Vucht (born in 1424), the daughter of John II of Loon, Lord of Jülich, Heinsberg and Löwenberg, on 7 February 1440.
They had children, including:
Anna of Nassau (1441–1514)
Johanna of Nassau (1444–1468)
Ottillie of Nassau (1445–1493)
Adriana of Nassau (1449–1477)
Engelbert II of Nassau (1451–1504)
Johann V of Nassau (1455–1516)