Trespass to land is a common law tort or crime that is committed when an individual or the object of an individual intentionally (or, in Australia, negligently) enters the land of another without a lawful excuse. Trespass to land is actionable per se. Thus, the party whose land is entered upon may sue even if no actual harm is done. In some jurisdictions, this rule may also apply to entry upon public land having restricted access. A court may order payment of damages or an injunction to remedy the tort.
By law, trespass for mesne profits is a suit against someone who has been ejected from property that did not belong to them. The suit is for recovery of damages the trespasser caused to the property and for any profits he or she may have made while in possession of that property.
For a trespass to be actionable, the tortfeasor must voluntarily go to a specific location but need not be aware that he entered the property of a particular person. If A forces B unwillingly onto C's land, C will not have action in trespass against B because B's actions were involuntary, but C may instead claim against A. Furthermore, if B is deceived by A as to the ownership or boundaries of C's land, A may be jointly liable with B for B's trespass.
In most jurisdictions, if a person were to accidentally enter onto private property, there would be no trespass, because the person did not intend any violation. However, in Australia, negligence may substitute the requirement for intent.
If a trespass is actionable and no action is taken within reasonable or prescribed time limits, the landowner may forever lose the right to seek a remedy, and may even forfeit certain property rights in the case of adverse possession and easement by prescription.
Trespass may also arise upon the easement of one person upon the land of another. For example, if A grants B a right to pass freely across A's land, then A would trespass upon B's easement by erecting a locked gate or otherwise blocking B's rightful access.