The Capet–Plantagenet feud is a series of conflicts and disputes that covers a period of 100 years (1159–1259) during which the House of Capet, rulers of the Kingdom of France, fight the House of Plantagenet (also known as the House of Anjou), rulers of the Kingdom of England, over the Plantagenet-held Angevin Empire which at its peak covers around half of the territory within France

Some historians refer to this series of events as the "First Hundred Years' War".

During the feud, the continental possessions of the Kings of England are considered to be more important than their insular ones, covering an area significantly greater than the territories controlled by the Kings of France who, however, are the overlords of the former in regards to the continental lands.

Indeed, while the Capetian's nominal suzerainty extends far beyond the small domain of Île-de-France, the actual power they hold over many of their vassals, including the Plantagenets, is weak.\

These reasons, in combination with the Plantagenet's hold on the sovereign kingdom of England adding to the strength of the Plantagenets, can be seen the primary reasons for the feud.

The feud between the two dynasties and the many wars that come with it lead to the gradual "reconquest" by the Capetians of most of their own kingdom, and later, the Plantagenet's attempts at retaking what they believe to be their rightful claims in western France.

After the conflict ends with the Treaty of Paris in 1259, the English kings, with regard to their few remaining possessions on the continent, would remain vassals to the French kings.

The Capetians are also able to consolidate their power, making the kingdom of France the wealthiest and most powerful state in medieval Western Europe.