Adverse possession—sometimes called squatter's rights—occurs when a person or entity who does not own a certain piece of real property occupies or uses it in a way that is adverse to the owner of the property—meaning the use is in conflict or at odds with the property owner’s interests.

If this adverse possession or use of the property meets the legal standard for adverse possession—often described as use that is continuous, exclusive, hostile, open, and notorious—and continues for the prescribed period of time (usually specified in the state statute)—the person or entity adversely possessing or using the property will acquire ownership of the property (title). This ownership will result in the changing of boundary lines.

Because the required adverse possession must be open, obvious, and adverse to the owner’s interests, title may only be acquired by adverse possession to the portion of property that is used in that way.

Adverse possession laws vary from state to state and may be located in a state’s court opinions (also known as common law or case law) or, more often, in its statutes.

In Ohio, adverse possession laws allow a person to claim ownership of a property if they have occupied it under certain conditions for a specific period of time. The requirements for adverse possession in Ohio are that the possession must be continuous, exclusive, open, notorious, and hostile for a period of 21 years, as per Ohio Revised Code Section 2305.04. The possession must be such that it would give the legal owner a cause of action for ejectment. The adverse possessor must treat the property as their own, without permission from the legal owner, and this use must be apparent to anyone. If all legal criteria are met, the adverse possessor can potentially acquire legal title to the property, which may result in changes to the boundary lines. It is important to note that adverse possession claims can be complex and typically require the involvement of an attorney to navigate the legal process.