The years in which the ‘Plantagenet’ counts of Anjou ruled Normandy (1144–1204) are usually regarded as a period of Norman decline. In 1144 the Angevin conquest of Normandy deprived the duchy of the dominant place which it had hitherto enjoyed within the Anglo-Norman regnum, and in 1204 the dukes of Normandy were ousted from the province completely. Thereafter the leaderless duchy became a supine dominion of the Capetian kings of France. The Normans retained a strong sense of provincial identity after 1204 and occasionally asserted their political weight, securing their famous charter of liberties, the Chartes aux Normands, during the revolt of the provincial leagues in 1314–15, but they never recovered the preponderant role they had enjoyed in the eleventh and early twelfth centuries. Nor did a new ducal family emerge, not even from the Capetian dynasty, although the Valois kings were later to make their eldest sons dukes of Normandy from time to time. In part, the province's decline reflected the more general eclipse of territorial principalities in France in the face of the rising Capetian monarchy. However, the history of Normandy after 1144 should not be seen merely as an appendix to a story of Norman greatness that ended in 1135. These six decades of Angevin rule were crucial to the establishment of enduring Norman customs and institutions, many of which lasted until the French Revolution – and in the Channel Islands survive even today.

Angevin Normandy has been curiously neglected by historians, but the reasons are not hard to find. Geoffrey of Anjou's subjugation of the duchy in 1144 was narrowly preceded by the death of Orderic Vitalis, and no narrative from the Angevin period matches his Ecclesiastical History as a source for Norman history. Most that survive are short annals; the only significant chronicler in Normandy was Robert of Torigny, abbot of Mont Saint-Michel (1154–86), whose chronicle is both laconic and prosaic. Torigny had previously added to the Gesta Normannorum Ducum, the text which had been rewritten to legitimise the reigning prince in almost every generation since Dudo of Saint-Quentin, but despite Torigny's initial plans he did not continue this work past the death of Henry I; nor did Gervase, prior of Saint-Cénery on the border of Normandy and Maine, whom Torigny urged to perform this task in his stead.