Trespass is an area of tort law broadly divided into three groups: trespass to the person, trespass to chattels, and trespass to land.

Trespass to the person historically involved six separate trespasses: threats, assault, battery, wounding, mayhem (or maiming), and false imprisonment. Through the evolution of the common law in various jurisdictions, and the codification of common law torts, most jurisdictions now broadly recognize three trespasses to the person: assault, which is "any act of such a nature as to excite an apprehension of battery"; battery, "any intentional and unpermitted contact with the plaintiff's person or anything attached to it and practically identified with it"; and false imprisonment, the "unlawful obstruction or deprivation of freedom from restraint of movement".

Trespass to chattel does not require a showing of damages. Simply the "intermeddling with or use of … the personal property" of another gives cause of action for trespass. Since CompuServe Inc. v. Cyber Promotions, Inc., various courts have applied the principles of trespass to chattel to resolve cases involving unsolicited bulk e-mail and unauthorized server usage.

Trespass to land is today the tort most commonly associated with the term trespass; it takes the form of "wrongful interference with one's possessory rights in [real] property". Generally, it is not necessary to prove harm to a possessor's legally protected interest; liability for unintentional trespass varies by jurisdiction. "At common law, every unauthorized entry upon the soil of another was a trespasser"; however, under the tort scheme established by the Restatement of Torts, liability for unintentional intrusions arises only under circumstances evincing negligence or where the intrusion involved a highly dangerous activity.

Trespass has also been treated as a common law offense in some countries.