It is a criminal offense to use or operate a motor vehicle, boat, airplane, motorcycle, or other motor-propelled vehicle without the consent of the owner or other person authorized to give consent. This crime is generally known as (1) unauthorized use of a motor vehicle, (2) unauthorized use of a vehicle, or (3) joyriding.

The difference between this crime and the crime of theft is that the state does not have to prove a person charged with unauthorized use of a motor vehicle intended to keep the vehicle or permanently deprive the owner of the vehicle.

Laws regarding the unauthorized use of a motor vehicle vary from state to state and are generally found in a state’s statutes—often in the penal or criminal code or the vehicle code.

In New Hampshire, unauthorized use of a motor vehicle, often referred to as 'joyriding,' is addressed under RSA 637:9, which is part of the state's criminal code. This statute makes it a misdemeanor for any person to take or operate another's vehicle without the owner's consent. The key distinction between this offense and vehicle theft (auto theft) is the element of intent. For a charge of unauthorized use, the state does not need to prove that the individual intended to permanently deprive the owner of the vehicle, which is a necessary element for a theft charge. Instead, the focus is on the unauthorized operation or use of the vehicle. Penalties for unauthorized use of a vehicle in New Hampshire may include fines, imprisonment, or both, depending on the circumstances and the individual's criminal history.