An appanage, or apanage (/ˈæpənɪdʒ/; French: apanage [apanaʒ] ^ⓘ), is the grant of an estate, title, office or other thing of value to a younger child of a monarch, who would otherwise have no inheritance under the system of primogeniture (where only the eldest inherits). It was common in much of Europe.

The system of appanage greatly influenced the territorial construction of France and the German states and explains why many of the former provinces of France had coats of arms which were modified versions of the king's arms.

Late Latin *appanaticum, from appanare or adpanare 'to give bread' (panis), a pars pro toto for food and other necessities, hence for a "subsistence" income, notably in kind, as from assigned land.

An appanage was a concession of a fief by the sovereign to his younger sons, while the eldest son became king on the death of his father. Appanages were considered as part of the inheritance transmitted to the puisné (younger sons). The word Juveigneur was specifically used for the royal princes holding an appanage. These lands returned to the royal domain (the territory directly controlled by the king) on the extinction of the princely line, and could not be sold (neither hypothetically nor as a dowry). Daughters were initially able to inherit the appanages under the Capetian kings. However, under the House of Valois, Salic law was applied, which prohibited women from inheriting.

The system of appanage has played a particularly important role in France. It developed there with the extension of royal authority from the 13th century, then disappeared from the late Middle Ages with the affirmation of the exclusive authority of the royal state. It strongly influenced the territorial construction, explaining the arms of several provinces. The prerogative of Burgundy is also the origin of the Belgian, Luxembourgeois and Dutch states, through the action of its dukes favored by their position in the court of the kings of France.

Primogeniture avoids territorial splintering, which the earlier Frankish tradition of partible inheritance (equal division) suffered from (e.g. under the Merovingians and subsequent Carolingians). But primogeniture creates resentment in younger sons who inherit nothing. Appanages thus were used to sweeten the bitter pill of primogeniture and deter revolt of younger sons by diverting their aspirations of claiming their eldest brother's throne.

Unlike their predecessors (the Carolingians), the Capetian dynasty's hold on the crown was initially tenuous. They could not afford to divide the kingdom among all their sons, and the royal domain was very small, initially consisting solely of the Île-de-France. So the Capetians broke away from the Frankish custom of partible inheritance, to instead have the eldest son alone become King and receive the royal domain (except for any appanages). Most Capetians endeavored to add to the royal domain through incorporation of additional fiefs, large or small, and thus gradually obtained direct lordship over almost all of France.

Their first king Hugh Capet (elected King of the Franks on the death of Louis V in 987) only had one son, Robert II. But Robert had multiple sons. One of them, Henry I of France, became the first king to create an appanage in 1032, when he gave the Duchy of Burgundy to his younger brother Robert I of Burgundy (whose descendants retained the duchy until 1361 with the extinction of the first Capetian House of Burgundy by the death of Philip de Rouvre).