Trespass to chattels is a tort whereby the infringing party has intentionally interfered with another person's chattel. The interference can be physical contact that harms the chattel in a quantifiable way, or any dispossession of the chattel (whether by taking it, destroying it, or barring the owner's access to it).
The origin of the concept comes from the original writ of trespass de bonis asportatis. As in most other forms of trespass, remedy can only be obtained once it is proven that there was direct interference regardless of damage being done, and the infringing party has failed to prove it was neither negligently or intentionally caused.
Damages from a trespass claim are limited to the actual harm sustained by the plaintiff. In cases of dispossession, the plaintiff is always entitled to damages if they can prove the dispossession occurred, even if no quantifiable harm can be proven.
A related tort is conversion, which involves an exercise of control over another's chattel justifying restitution of the chattel's full value. Some actions constitute trespass and conversion; in these cases, a plaintiff must choose which claim to make based on what amount of damages they seek to recover.