In the nineteenth and early twentieth century it was assumed that nearly all agricultural labourers in medieval Europe were serfs. Serfdom was distinct from slavery in that serfs were recognized as something more than chattels. They could contract legitimate marriages, hold personal property and they could not be moved around at will. In fact, so closely were they tied to the land they tilled that they were prohibited from leaving it. Thus serfs were unfree in the sense of being dependents of their landlords and these landlords controlled many aspects of their lives, but serfs had a degree of communal, familial and individual identity and autonomy. There is no modern, synthetic book on medieval serfdom that compares regions or draws general conclusions about it. This work attempts such a synthesis and also shows avenues of future research, but most importantly it is intended to reorient attention to the importance of serfdom in the structure of medieval society.