Count Maurice Frederick of Nassau-Siegen (19 January 1621 – 17 June 1638), German: Moritz Friedrich Graf von Nassau-Siegen, official titles: Graf zu Nassau, Katzenelnbogen, Vianden und Diez, Herr zu Beilstein, was a count from the House of Nassau-Siegen, a cadet branch of the Ottonian Line of the House of Nassau.

Maurice Frederick was born at Siegen Castle [de][1] on 19 January 1621[2][note 1] as the second son of Count William of Nassau-Siegen and Countess Christiane of Erbach.

[4] Maurice Frederick became a student at Leiden University on 3 September 1633,[5][6] and on 27 May 1636 he was appointed captain of a infantry company in the Dutch States Army,[5] where his father was field marshal.

William conquered the sconces of Stabroek and Calloo and chased off the Spaniards, but instead of continuing his march, he reinforced himself on the spot.

When he heard the false rumour that the Spaniards were approaching with a greater force than his own, he fled in confusion.