Mortmain refers to the ownership of land by a corporation. It literally means dead hand in French, because land owned by a corporation keeps its status in perpetuity. Mortmain is a historical term that arose during the Middle Ages in England, when it generally referred to land owned by the Catholic Church or one of its religious communities.
The right of the Church to own land had been recognized since the reign of Constantine in the 3rd century, but the situation became unpopular under the feudal system, as it deprived feudal lords from any revenue from the land in question. Under the feudal system, landowners has to pay incidents or taxes whenever the land changed hands, as upon the death of a landowner.
In addition, the lord became the guardian of any underage landholder and held the right to choose who a female heir would marry. If a landowner lost the land, such as by dying without naming an heir or by committing a felony, the property's ownership reverted to the lord. The English crown was the ultimate owner of all land in the country, and therefore the ultimate lord, with other lords acting as mediates between lesser landowners and the Crown.
While the Church's right to own land had been limited in documents including the Magna Carta of 1215 and the 1259 Provisions of Westminster, King Edward I's Statutes of Mortmain more clearly defined the law. Under these statutes, enacted in 1279 and 1290, property could only come under the control of a corporation if the Crown authorized it. The Statutes of Mortmain are an important part of legal history, but laws against mortmain no longer exist in most countries. The rule against perpetuities in modern trust law, which prevents people from granting property to descendents far in the future, is similar to earlier laws against mortmain.