Haps·burg also Habs·burg (hāps'bûrg', häps'bŏŏrk') A royal German family that supplied rulers to a number of European states from the late Middle Ages until the 20th century. The Hapsburgs reached the height of their power under Charles V of Spain. When Charles abdicated (1558), the empire was divided between the Spanish and Austrian lines. The Spanish branch ceased to rule after 1700 and the Austrian branch after 1918.