Ho·hen·zol·lern (hō'ən-zŏl'ərn, -tsôl'-) German royal family who ruled Brandenburg from 1415 and later extended their control to Prussia (1525). Under Frederick I (ruled 1701-1713) the family's possessions were unified as the kingdom of Prussia. From 1871 to 1918 Hohenzollern monarchs ruled the German Empire.