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 Oklahoma, adverse possession laws allow a person to claim ownership of property not legally theirs if they meet certain criteria. The possession must be continuous, exclusive, hostile, open, and notorious. Oklahoma statutes require a 15-year period of such possession for a claim of adverse possession to be valid, under Title 12, Section 93 of the Oklahoma Statutes. However, if the adverse possessor pays the property taxes during the period of possession, the required period is reduced to 7 years, as per Title 60, Section 333 of the Oklahoma Statutes. The claimant must treat the property as their own, without permission from the legal owner, and their use of the property must be so visible and apparent that it gives notice to the legal owner that someone is asserting a claim against their property. If these conditions are met, the adverse possessor may be able to acquire legal title to the property, potentially altering the boundary lines. It is important to note that adverse possession claims can be complex and often require the involvement of an attorney to navigate the legal process.