中世紀歐洲佃農被束縛在承襲的一塊土地上對地主唯命是從的狀況。農奴與奴隸的區別在於，奴隸的買賣與土地無關，而農奴只有在所勞作的土地被轉手以後，農奴才會更換主人。約從2世紀起，羅馬帝國原來由一批批奴隸耕作的大片私有土地已被打散，交由農民耕種。這些農民便開始依靠較大的地主，以免受亂世之害，而發誓效忠於領主也成為一種普遍行為。332年君士坦丁一世要求佃農為地主提供勞務，並使得農奴制合法化。農奴不能結婚，不能改變職業，在沒有地主允許的情況下，也不能遷移，還必須把收成的大部分上交給地主。中央集權的政治勢力的發展，由黑死病造成的勞動力短缺，以及14～15世紀的地方農民起義使得西歐的農奴逐漸被解放。而在這一時期，東歐的農奴制卻變得更加堅實，奧匈帝國的農民直到18世紀末才得以解放，俄國的農奴1861年得以解放。亦請參閲feudalism。
serfdom
Condition in medieval Europe in which a tenant farmer was bound to a hereditary plot of land and to the will of his landlord. Serfs differed from slaves in that slaves could be bought and sold without reference to land, whereas serfs only changed lords when the land they worked changed hands. From about the 2nd century AD, large privately owned estates in the Roman empire that had been worked by slaves were broken up and given to peasant farmers. These farmers came to depend on larger landowners for protection in turbulent times, and swearing fealty to a proprietor became common practice. In 332 Constantine I established serfdom legally by requiring the tenant farmers to pay labor services to their lords. As serfs, they could not marry, change occupations, or move without their lord's permission, and they had to give a major portion of their harvest to their lord. The development of centralized political power, the labor shortage brought about by the Black Death, and endemic peasant uprisings in the 14th-15th century led to the gradual emancipation of serfs in Western Europe. In Eastern Europe serfdom became more entrenched during that period; the peasants of the Austro-Hungarian empire were not freed until the late 18th century, and Russia's serfs were not freed until 1861. See also feudalism.
