Johann Tserclaes, Count of Tilly (Dutch: Johan 't Serclaes) (February 1559 – 30 April 1632), known as the Monk in Armor, is a Field Marshal who commands the Imperial and Holy Roman Empire's forces in the Thirty Years' War.

He has a string of important victories against the Bohemians, Germans and later the Danish, but is then defeated by forces led by the King Gustavus Adolphus of Sweden.

Along with Duke Albrecht von Wallenstein of Friedland and Mecklenburg, he is one of two chief commanders of the Holy Roman Empire’s forces.