The California Highway Patrol (CHP) is the principal state police agency for the U.S. state of California. The CHP has primary jurisdiction, including patrol and investigations, over all California freeways and state property. Additionally, the CHP is responsible for the enforcement of all laws regulating the operation of vehicles on highways, including all roadways, outside incorporated city limits. The CHP can exercise law enforcement powers anywhere within the state.

The California State Legislature originally established the California Highway Patrol as a branch of the Division of Motor Vehicles in the Department of Public Works, with legislation signed by Governor C. C. Young on August 14, 1929. It was subsequently established as a separate department with legislation signed by Governor Earl Warren in 1947. The CHP gradually assumed increased responsibility beyond the enforcement of the State Vehicle Act and eventually absorbed the smaller California State Police in 1995. It is currently organized as a department under the California State Transportation Agency (CalSTA).

In addition to its highway patrol duties, the CHP also provides other services including protecting state buildings and facilities (most notably the California State Capitol) and guarding state officials. The CHP also works with municipal and federal law enforcement agencies, providing assistance in investigations, patrol and other aspects of law enforcement.

The California Highway Patrol is the largest state police agency in the United States, with 11,000 employees, over 7,600 of whom are sworn, according to a study in December 2019.

The CHP gained international recognition in the late 1970s and the early 1980s, through the broadcast of the TV series CHiPs, which chronicled the adventures of two fictional CHP motorcycle officers.

The CHP is responsible for public safety and law enforcement on all freeways and expressways, throughout the state, regardless of whether the freeway is within the boundaries of an incorporated city. Additionally, the CHP is responsible for the enforcement of all laws regulating the operation of vehicles, and the use of the highways and public roads in unincorporated portions of a county. Local police or the local sheriff's department having a contract with an incorporated city are primarily responsible for investigating and enforcing traffic laws within the boundaries of an incorporated city; however, any peace officer of the CHP may enforce any state law anywhere within the state, even though the agency's primary mission is related to transportation. Furthermore, CHP officers act as bailiffs for the California Supreme Court and the six California Courts of Appeal, and also provide security at buildings occupied by the State of California.

CHP officers enforce the California Vehicle Code, pursue fugitives spotted on the highways, and attend to all significant obstructions and crashes within their jurisdiction. CHP officers are responsible for investigating and disposing of car accidents, disabled vehicles, debris, and other impediments to the flow of traffic. They are often the first responders at the scene of an accident (or obstruction), and in turn summon paramedics, firefighters, tow truck drivers, or Caltrans personnel. The CHP files traffic crash reports for state highways and within unincorporated areas. The CHP responds to and investigates all accidents involving school buses throughout the state including incorporated cities.

CHP also has Multidisciplinary Accident Investigation Teams (MAIT) for the investigation of complex traffic crashes.