Count Henry III of Nassau-Dillenburg-Dietz (January 12, 1483, Siegen – September 14, 1538, Breda), Lord (from 1530 Baron) of Breda, Lord of the Lek, of Dietz, etc., is a count of the House of Nassau.

He is the son of Count John V of Nassau-Dillenburg and Elisabeth of Hesse-Marburg.

His younger brother is William I, Count of Nassau-Dillenburg (the father of William the Silent).