A prescriptive easement—also known as an easement by prescription or an adverse easement—is an easement (right to use property) created by a use of property (the servient estate) that is open, continuous, and adverse to the owner of the property (the servient estate).

To satisfy the requirement that the use be continuous, the use must take place over a required period of time—which may be specified in a state’s court opinions (common law or case law) or in its statutes if the state legislature has written the law regarding easements into statutes or code. If the state legislature has written a law in statutes or codes the law is said to be codified.

In Washington State, a prescriptive easement is recognized and can be established when a person uses another's property in a manner that is open, notorious, continuous, and hostile for a statutory period. The statutory period required for a prescriptive easement in Washington is ten years, as per RCW 7.28.050. This means that the person claiming the easement must have used the property in such a manner for at least ten years without the permission of the property owner. The use must be such that the property owner could reasonably be expected to notice it (open and notorious), it must not be interrupted (continuous), and it must be without the owner's permission (hostile). If these conditions are met, the person using the land may have a legal right to continue doing so, even without the owner's consent. It is important to note that the specifics of each case can vary, and establishing a prescriptive easement can be complex, often requiring the assistance of an attorney.