A northern French duchy founded from Viking settlement and central to the Norman Conquest of England.
Normandy began as a Viking settlement legalised: in 911, by the traditional grant of Saint-Clair-sur-Epte, the Carolingian king Charles the Simple ceded the lower Seine to the Norse leader Rollo, whose descendants turned raiders' land into the most precociously governed principality in France.
From it came the eleventh century's most consequential conquest — William the Conqueror's England, 1066 — and a cross-Channel realm whose duke-kings ruled from the Tyne to the Loire until Philip II Augustus took the duchy in 1204; thereafter Normandy was the French crown's richest province, England's target renewed in the Hundred Years' War (occupied 1417–1450), and the stage of the war's Norman decision at the Battle of Formigny.
The Seine valley bore the worst of the ninth century's Viking storm — Rouen burned, Paris besieged — until royal policy tried enfeoffment: Rollo's band received Rouen and its county in 911 against baptism and defence of the river, and successive grants (924, 933) pushed "the Northmen's land" to roughly its historic borders. Assimilation was startlingly fast: within two generations the ducal family spoke Romance, married Frankish, and ruled through counts, viscounts, and a restored church.
Dukes Richard I and II made the duchy a power — allying with Capetians, marrying into England (Emma, wed to Æthelred the Unready, then to Cnut the Great), and rebuilding the abbeys (Fécamp, Jumièges, Mont-Saint-Michel) whose schools, under imports like William of Volpiano and Lanfranc at Bec, gave Normandy Europe's most vigorous new monastic culture.
William the Bastard's minority (from 1035) nearly dissolved the duchy in baronial anarchy; his victory at Val-ès-Dunes (1047) and twenty years of siege-war rebuilt it into the disciplined instrument that crossed the Channel: castles licensed by the duke alone, a church reformed under his half-brother Odo of Bayeux and Archbishop Maurilius, knight-service quotas that read like an army list. The Battle of Hastings in 1066 made the duke a king and Normandy the senior partner of a cross-Channel state.
The realm's double structure — barons holding on both shores, succession disputes splitting them — set the next century's pattern: William's sons fought over the halves (Robert Curthose losing Normandy to William II Rufus's pawn and then to Henry I's conquest at Tinchebray, 1106); Stephen's anarchy lost the duchy to Anjou (Geoffrey Plantagenet, 1144); and under Henry II Normandy anchored the Angevin empire, its exchequer at Caen and its customs (the Très Ancien Coutumier appearing c. 1200) the empire's administrative model.
Philip II Augustus took the duchy from King John in 1202–1204 — Château Gaillard's six-month siege the epic, Rouen's surrender in June 1204 the end — and the annexation held: the Norman church, towns, and custom kept their privileges under Capetian rule, codified when the crown confirmed the Charte aux Normands in 1315, the province's Magna Carta. For two centuries French Normandy was the monarchy's fiscal heartweight and its window on the Channel war.
Henry V renewed the old claim in arms: Harfleur (1415) and the Agincourt campaign, then the methodical conquest of 1417–1419 climaxing at the Siege of Rouen, gave Lancastrian England the whole duchy — governed from Rouen for thirty years, with a university founded at Caen (1432) and Norman estates voting taxes, but bleeding under the écorcheur war and the resistance the occupation bred. Charles VII's reconquest of 1449–1450 swept it away in a year: Rouen opened its gates, the relief army died at the Battle of Formigny in April 1450, and Cherbourg's fall that August ended English Normandy forever.
Rollo, c. 911–927 — the Viking founder, baptised Robert: legend's hard bargainer at Saint-Clair-sur-Epte.
Richard II, 996–1026 — the duchy's consolidator; Emma's brother, the abbeys' rebuilder.
William the Conqueror, duke 1035–1087 — Val-ès-Dunes, Hastings, and the cross-Channel realm.
Robert Curthose, 1087–1106 — crusader and loser of Tinchebray; died England's prisoner.
Henry I of England, duke 1106–1135 — the Anglo-Norman state at its administrative height.
Henry II of England, duke 1150–1189 — Normandy as the Angevin empire's hinge.
John of England, duke to 1204 — the loser of the duchy.
Henry V of England, conqueror 1417–1422 — the Lancastrian duchy's architect.
Norman culture fused Norse energy with Frankish and Latin form. Its architecture named a style: Jumièges and Caen's twin abbeys (Saint-Étienne and La Trinité, the Conqueror's and Matilda's penance-houses) rehearsed the Romanesque England would build big; Mont-Saint-Michel piled Gothic on its rock; the Bayeux Tapestry — commissioned in the conquest generation, probably for Odo of Bayeux — remains the Middle Ages' most famous narrative object.
The duchy's schools travelled: Bec under Lanfranc and Anselm supplied Canterbury its greatest archbishops; Norman adventurers supplied the Mediterranean its newest kings — the Hauteville brothers conquering southern Italy and Sicily (Roger II crowned 1130), Bohemond taking Antioch on the First Crusade — so that "Norman" named a world from Durham to Palermo. At home, customary law hardened early (the coutumiers, the exchequer's rolls), and the towns — Rouen's commune chartered under the Angevins, its Établissements copied across the west — ran Europe's densest cloth-and-river economy between Paris and the sea.