Serfdom was a condition of debt bondage and indentured servitude that was common in medieval Europe under feudalism, specifically relating to manorialism and similar systems. It was a system in which a tenant farmer was bound to a hereditary plot of land and to the will of his landlord. The vast majority of serfs in medieval Europe obtained their subsistence by cultivating a plot of land that was owned by a lord. The serf provided his own food and clothing from his own productive efforts, but a substantial proportion of the grain the serf grew on his holding had to be given to his lord. The lord could also compel the serf to cultivate that portion of the lord’s land that was not held by other tenants (called demesne land). The serf also had to use his lord’s grain mills and no others.

Serfs had a specific place in feudal society, as did barons and knights: in return for protection, a serf would reside upon and work a parcel of land within the manor of his lord. Thus, the manorial system exhibited a degree of reciprocity. However, the essential additional mark of serfdom was the lack of many of the personal liberties that were held by freedmen. Chief among these was the serf’s lack of freedom of movement; he could not permanently leave his holding or his village without his lord’s permission. Neither could the serf marry, change his occupation, or dispose of his property without his lord’s permission. He was bound to his designated plot of land and could be transferred along with that land to a new lord. Serfs were often harshly treated and had little legal redress against the actions of their lords.

The word "serf" originated from the Middle French serf and was derived from the Latin servus ("slave"). In Late Antiquity and most of the Middle Ages, what are now called serfs were usually designated in Latin as coloni. As slavery gradually disappeared and the legal status of servi became nearly identical to that of the coloni, the term changed meaning into the modern concept of "serf". Forms of serfdom varied greatly through time and across different societies.