The Newhall incident, also called the Newhall massacre, was a shootout on April 5–6, 1970, in Valencia, California, between two heavily armed criminals and four officers of the California Highway Patrol (CHP). In less than five minutes, the four CHP officers were killed in the deadliest day in California law enforcement history.At about 11:54 p.m. on April 5, CHP officers Walt Frago and Roger Gore conducted a traffic stop of Bobby Davis and Jack Twinning in conjunction with an incident reported to the CHP minutes earlier. Twinning and Davis initially cooperated with the officers but then opened fire, killing both of them. Moments later, officers George Alleyn and James Pence arrived on the scene and engaged Twinning and Davis in a shoot out. A bystander tried to help by firing an officer's weapon, but the three were out-gunned. Both Alleyn and Pence suffered fatal injuries, while the witness ran out of ammunition and took cover in a ditch. A third CHP patrol car arrived on scene, and the officers briefly exchanged gunfire with the perpetrators, who then fled.

Davis stole a car and attempted to flee the area, but he was spotted by police and arrested. Meanwhile, Twinning broke into a house, taking an occupant hostage. It was surrounded by deputies of the Los Angeles County Sheriff's Department, and Twinning released the hostage. He committed suicide around 9 a.m. as the deputies entered the house. Davis was convicted and sentenced to death for the murders. His sentence was commuted to life imprisonment without the possibility of parole in 1972; he killed himself at Kern Valley State Prison in 2009.

The Newhall incident resulted in a number of changes at the CHP, including procedural changes for arresting high-risk suspects, standardization of firearms, and firearms training used throughout the department.