When did the Duchy of Normandy exist?

The Duchy of Normandy existed 911–1204/1259. On this map it is drawn AD 922–1071.

How large was the Duchy of Normandy?

At its greatest extent drawn on this map, the Duchy of Normandy covered about 39,000 km². That is the largest area the border data gives it across the years it is drawn, not necessarily its greatest extent in history.

Europe · The early medieval west

Duchy of Normandy

911–1204/1259

Duché de Normandie; Norman Duchie de Normaundie; Latin Ducatus Normanniae. Named for the Normanni ("Northmen").

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Existed: 911–1204/1259
Shown on the map: AD 922–1071
Peak area: 39k km²
Region: Europe

Names

Duché de Normandie; Norman Duchie de Normaundie; Latin Ducatus Normanniae. Named for the Normanni ("Northmen"). Capital: Rouen.

Foundation

The duchy originated in the grant of land around Rouen by King Charles III "the Simple" of West Francia to the Viking leader Rollo, conventionally by the Treaty of Saint-Clair-sur-Epte (911) following Rollo's failed siege of Chartres; Rollo agreed to convert, do homage, and defend the Seine against other Vikings. Contested-source note: no contemporary text of the treaty survives; the detailed narrative comes from Dudo of Saint-Quentin's Gesta Normannorum (composed c. 996–1026), commissioned by Rollo's descendants. As the historian Fraser McNair observes, Dudo is "the only person who actually puts a date on the agreement made between Charles the Simple and Rollo … whose chronology is dreadful," and Wikipedia summarizes the scholarly consensus that "Dudo is a highly unreliable source who may have written his chronicle primarily as a didactic tool to teach courtly values." The traditional 911 date thus rests on Dudo alone, and historians have at times doubted the treaty's very existence, though a charter of 918 confirms the land grant.

Rulers

Rollo (c. 911–927) was succeeded by his male-line and then cognatic descendants. The most famous, William the Conqueror (Duke 1035–1087), conquered England in 1066, after which the dukes were usually also kings of England — exceptions being Robert Curthose (1087–1106), Geoffrey Plantagenet (who conquered Normandy 1144) and Henry II before he became king (1154). The last effective duke was John (1199–1204).

Fall

In 1202 Philip II, as feudal suzerain, declared Normandy forfeit; his armies overran it by 1204 (the fall of Château Gaillard, March 1204, being decisive), and continental Normandy was annexed to the royal demesne. England renounced its claim in the Treaty of Paris (1259). The Channel Islands remained attached to the English crown as the last remnant, splitting into the Bailiwicks of Guernsey and Jersey by 1290; they remain British Crown Dependencies today.

Significance

Normandy produced one of the most dynamic aristocracies of the medieval West, conquering England and (as a separate movement) southern Italy and Sicily, and pioneering administrative techniques (the Exchequer) later exported to England.

Common questions

What was the Duchy of Normandy?: Duché de Normandie; Norman Duchie de Normaundie; Latin Ducatus Normanniae. Named for the Normanni ("Northmen").
When did the Duchy of Normandy exist?: The Duchy of Normandy existed 911–1204/1259. On this map it is drawn AD 922–1071.
How large was the Duchy of Normandy?: At its greatest extent drawn on this map, the Duchy of Normandy covered about 39,000 km². That is the largest area the border data gives it across the years it is drawn, not necessarily its greatest extent in history.
Who ruled the Duchy of Normandy?: Rollo (c. 911–927) was succeeded by his male-line and then cognatic descendants. The most famous, William the Conqueror (Duke 1035–1087), conquered England in 1066, after which the dukes were usually also kings of England — exceptions being Robert Curthose (1087–1106), Geoffrey Plantagenet (who conquered Normandy 1144) and Henry II before he became king (1154).
How did the Duchy of Normandy end?: In 1202 Philip II, as feudal suzerain, declared Normandy forfeit; his armies overran it by 1204 (the fall of Château Gaillard, March 1204, being decisive), and continental Normandy was annexed to the royal demesne. England renounced its claim in the Treaty of Paris (1259).
Why does the Duchy of Normandy still matter?: Normandy produced one of the most dynamic aristocracies of the medieval West, conquering England and (as a separate movement) southern Italy and Sicily, and pioneering administrative techniques (the Exchequer) later exported to England.

Sources

This compendium cites its sources once for the whole document rather than per territory. Its bibliography names the English Wikipedia articles for each territory as the primary basis, cross-checked against Encyclopædia Britannica and specialist snippets, and flags entries built on unreliable foundations — the 911 treaty of Saint-Clair-sur-Epte known only from Dudo of Saint-Quentin, and Arnaud Amalric's alleged order at Béziers attested only decades after the fact. The article this entry is anchored on:

Wikipedia — Duchy of Normandy en.wikipedia.org/wiki/Duchy_of_Normandy

This entry was last updated 27 September 2026.

This entry was researched and drafted with AI from the sources above, and has not been reviewed by a historian. How entries are made

Text available under CC BY-SA 4.0: reuse it with a credit to The World Through Time and a link to this page. Passages drawing on the Wikipedia articles listed above are also licensed CC BY-SA 4.0 by their contributors.

Border geometry for the map itself comes from Cliopatria v0.12 (Seshat Global History Databank, CC-BY-4.0).

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