Trespass is the unauthorized entry upon the land (real property) of another. Trespass may occur when one enters—or causes something to enter—another's property without permission. The law has traditionally recognized a claim or cause of action for damages based on trespass.

The owner of real property generally has the right to exclude all others from use of the property—although this right to exclude others may be relinquished in limited circumstances, such as when there is an easement allowing another to use the property. As a general rule, any unauthorized entry upon land of another is a trespass even when there is no damage or only slight damage.

Thus, to prove a trespass claim, the plaintiff must show that it owned the property or had a right to exclude others from the property. Some courts have recognized that the right to explore for oil and minerals is a valuable property right that can be legally protected through a trespass claim.

To recover damages for trespass to real property, a plaintiff must prove that: (1) the plaintiff owned or had a lawful right to possess real property; (2) the defendant entered the plaintiff’s land and the entry was physical, intentional, and voluntary; and (3) the defendant’s trespass caused injury to the plaintiff’s right of possession.

The only relevant intent is that of the actor (defendant) to enter the property. The actor’s subjective intent or awareness of the property’s ownership is irrelevant.

In Idaho, trespassing is defined as the unauthorized entry onto another person's land without permission. The law in Idaho recognizes trespass as a civil wrong (a tort) that can lead to a claim for damages. To establish a trespass claim in Idaho, a plaintiff must demonstrate that they owned the property or had the right to exclude others from it, that the defendant intentionally and voluntarily entered the property, and that the entry resulted in injury to the plaintiff's right of possession. It is important to note that the defendant's intent to enter the property is what matters, not their knowledge or awareness of the property's ownership status. If the trespass involves the exploration for or extraction of oil and minerals, this can also be protected under trespass law, as these rights are considered valuable property interests in Idaho. The property owner has the right to exclude others, but this right can be waived in certain situations, such as when an easement exists. Damages for trespass can include compensation for any harm done to the property or the owner's possessory interests.