The title "Duke of Normandy" refers to the ruler of the historical region of Normandy in northern France. Established in the 10th century, the duchy was created when the Viking leader Rollo was granted land by the French king. The title became significant as it was held by several notable figures, including William the Conqueror, who later became the King of England after his successful invasion in 1066. The Duke of Normandy played a crucial role in the feudal system, overseeing land and vassals within the duchy. The title has evolved over time, and today, it is associated with the British royal family, as the current monarch holds the title as part of their heritage.