In the United States, the state police is a police body unique to each U.S. state, having statewide authority to conduct law enforcement activities and criminal investigations. In general, state police officers or highway patrol officers, known as state troopers, perform functions that do not fall within the jurisdiction of a county’s sheriff, such as enforcing traffic laws on state highways and interstates, overseeing security of state capitol complexes, protecting governors, training new officers for local police forces too small to operate an academy and providing technological and scientific services. They also support local police and help to coordinate multi-jurisdictional task force activity in serious or complicated cases in states that grant full police powers statewide.

State police, provincial police or regional police are a type of sub-national territorial police force found in nations organized as federations, typically in North America, South Asia, and Oceania. These forces typically have jurisdiction over the relevant sub-national jurisdiction, and may cooperate in law enforcement activities with municipal or national police where either exist.