John Maurice of Nassau (Dutch: Johan Maurits van Nassau-Siegen; German: Johann Moritz von Nassau-Siegen, Portuguese: João Maurício de Nassau-Siegen, June 17, 1604 – 20 December 1679), called "the Brazilian", is count and (from 1674) prince of Nassau-Siegen, and Grand Master of the Order of Saint John (Bailiwick of Brandenburg).