The Duke of Lorraine was a title held by the rulers of the historical region of Lorraine in northeastern France. The duchy emerged in the 10th century and became significant during the Middle Ages, especially due to its strategic location between France and Germany. The dukes played a crucial role in regional politics and conflicts, particularly during the Hundred Years' War and the Thirty Years' War. The title of Duke of Lorraine was held by various noble families, most notably the House of Lorraine. In 1737, the last duke, Francis Stephen, became Holy Roman Emperor, leading to the eventual integration of Lorraine into France in 1766. The legacy of the dukes is still evident in the cultural and historical identity of the region.