A vassal or feudatory is a person who has entered into a mutual obligation to a lord or monarch in the context of the feudal system in medieval Europe. The obligations often included military support and mutual protection, in exchange for certain privileges, usually including the grant of land held as a fiefdom. The term can be applied to similar arrangements in other feudal societies. In contrast, a fidelity, or fidelitas, was a sworn loyalty, subject to the king.

Western vassalage

In fully developed vassalage, the lord and the vassal would take part in a commendation ceremony composed of two parts, the homage and the fealty, including the use of Christian sacraments to show its sacred importance. According to Eginhard's brief description, the commendatio made to Pippin the Younger in 757 by Tassillo, Duke of Bavaria, involved the relics of Saints Denis, Rusticus, Éleuthère, Martin, and Germain – apparently assembled at Compiègne for the event. Such refinements were not included from the outset when it was time of crisis, war, hunger, etc.. Under feudalism, those who were weakest needed the protection of the knights who owned the weapons and knew how to fight. Feudal society was increasingly based on the concept of "lordship" (French seigneur), which was one of the distinguishing features of the Early Middle Ages and had evolved from times of Late Antiquity.