In English law, a fee simple (or fee simple absolute) is an estate in land, a form of freehold ownership. It is the way that real estate is owned in common law countries, and is the highest ownership interest possible that can be had in real property. Allodial title is reserved to governments under a civil law structure. Fee simple ownership represents an ownership interest in real property, though it is limited by government powers of taxation, eminent domain, police power, and escheat, and it could also be limited further by certain encumbrances or conditions in the deed.^{[citation needed]} Fee simple ownership interest may be limited by government powers through a shift from allodial title to fee simple, such as when uniting with other property owners acceding to zoning restrictions and municipal regulation.^{[citation needed]}

The word "fee" is derived from fief, meaning a feudal landholding. Feudal land tenures existed in several varieties, most of which involved the tenant having to supply some service to his overlord, such as knight-service (military service). If the tenant's overlord was the king, Grand Serjeanty, then this might require providing many different services, such as providing horses in time of war or acting as the king's ceremonial butler. These fiefs gave rise to a complex relationship between landlord and tenant, involving duties on both sides. For example, in return for receiving his tenant's fealty or homage, the overlord had a duty to protect his tenant. When feudal land tenure was abolished all fiefs became "simple", without conditions attached to the tenancy.