Count Henry III of Nassau-Dillenburg-Dietz (12 January 1483, Siegen – 14 September 1538, Breda), Lord (from 1530 Baron) of Breda, Lord of the Lek, of Dietz, etc.
was a count of the House of Nassau.
He was the son of Count John V of Nassau-Dillenburg and Elisabeth of Hesse-Marburg.
His younger brother was William I, Count of Nassau-Dillenburg (the father of William the Silent).