King Frederick III of Denmark reigned from 1648 until his death in 1670. He was a member of the House of Oldenburg and is known for establishing absolute monarchy in Denmark, which centralized power in the hands of the king. His reign saw significant military conflicts, including the Second Northern War, which affected Denmark's territorial holdings. Frederick III was also a patron of the arts and education, promoting cultural development in Denmark. He is remembered for his efforts to strengthen the Danish state and for his role in shaping the future of the Danish monarchy, influencing his successors like King Christian V.