The Duke of Oldenburg is a title associated with the historical region of Oldenburg in northern Germany. The title has been held by various members of the House of Oldenburg, a noble family that played a significant role in European history. The dukedom was established in the 12th century and has connections to several other royal families across Europe. The last reigning Duke of Oldenburg was Frederick Augustus II, who ruled until 1918. After the end of the monarchy in Germany, the title became largely ceremonial. Today, descendants of the House of Oldenburg still exist, and the title is often used in a historical context.