Frederick II of Germany, also known as Frederick Barbarossa, was a Holy Roman Emperor who reigned from 1155 until his death in 1190. He is best known for his efforts to consolidate the empire and strengthen its authority over the Italian city-states. Frederick sought to restore the glory of the Holy Roman Empire and was involved in several military campaigns in Italy. Frederick II was a key figure in the Crusades, participating in the Third Crusade and negotiating with Muslim leaders. His reign was marked by conflicts with the papacy and local nobles, which shaped the political landscape of medieval Europe. Frederick's legacy includes his promotion of culture and law, influencing future generations of rulers.