The Duchy of Normandy grew out of the 911 Treaty of Saint-Clair-sur-Epte between King Charles III of West Francia and the Viking leader Rollo. The duchy was named for its inhabitants, the Normans.
Statue of Rollo, founder of the fiefdom of Normandy, standing in Falaise, Calvados, birthplace of his descendant William the Conqueror, the Duke of Normandy who became King of England
"La Reine, Notre Duc": title of a Diamond Jubilee exhibition at the Jersey Arts Centre
Treaty of Saint-Clair-sur-Epte
The treaty of Saint-Clair-sur-Epte (911) is the foundational document of the Duchy of Normandy, establishing Rollo, a Norse warlord and Viking leader, as the first Duke of Normandy in exchange for his loyalty to Charles III, the king of West Francia, following the Siege of Chartres. The territory of Normandy centered on Rouen, a city in the Marches of Neustria which had been repeatedly raided by Vikings since the 840s, and which had finally been taken by Rollo in 876.
Kingdom of France in the late 10th century; the Duchy of Normandy is marked Duché de Normandie, and the royal domain is blue.