Hirsau Abbey, formerly known as Hirschau Abbey, was once one of the most important Benedictine abbeys of Germany. It is located in the Hirsau borough of Calw on the northern slopes of the Black Forest mountain range, in the present-day state of Baden-Württemberg. In the 11th and 12th century, the monastery was a centre of the Cluniac Reforms, implemented as "Hirsau Reforms" in the German lands.