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 Massachusetts, adverse possession laws allow a person to claim ownership of a property if they have occupied it in a manner that is open, notorious, continuous, exclusive, and hostile for a period of 20 years. This means the occupant must use the property as if they are the owner, without permission from the actual owner, and their occupation must be obvious to anyone, including the owner. If these conditions are met for the full 20-year period, the occupant may be able to acquire legal title to the property. The concept of adverse possession in Massachusetts is intended to encourage landowners to actively maintain and defend their property rights. It's important to note that adverse possession claims can be complex and fact-specific, and anyone considering or facing such a claim should consult with an attorney to understand their rights and obligations under Massachusetts law.