Countess Mary of Nassau-Siegen, German: Maria Gräfin von Nassau-Siegen, official titles: Gräfin zu Nassau, Vianden und Diez, Frau zu Breda, was a countess from the House of Nassau-Siegen, a cadet branch of the Ottonian Line of the House of Nassau, and through marriage Countess of Nassau-Wiesbaden-Idstein. Wikipedia