trespass, in law, any physical injury to the person or to property. In English common law the action of trespass first developed (13th cent.) to afford a remedy for injuries to property. The two early forms were trespass quare clausum fregit, used in instances of breaking into real property, and trespass de bonis asportatis, used when personal property was removed without consent. To sue for trespass the plaintiff must have had possession of the property. Although the offense of trespass required the use of force, the courts quickly decided that the mere act of breaking in or of taking goods was in itself forceful. Trespass in time was applied to injuries to the person involving force, such as assault, battery, and unlawful imprisonment. Out of the law of trespass developed many of the torts that are now commonly recognized. In present-day usage the term trespass is usually applied only to unlawful entry into private property. If a trespasser refuses a request to leave the premises, he may be removed by force.

In law, unlawful entry onto land. Trespass was formerly defined as wrongful conduct causing injury or loss; today it is generally confined to issues involving real property (see real and personal property). Once a trespass is proved, the trespasser is usually held liable for any damages resulting, regardless of whether the trespasser was negligent or the damage was foreseeable. Criminal trespass, trespass to property that is forbidden by statute, is punishable as a crime.

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