Four police officers in Oakland, California, were fatally shot on March 21, 2009, by Lovelle Mixon, a convicted felon wanted on a no-bail warrant for a parole violation. Mixon shot and killed two police officers of the Oakland Police Department during a routine traffic stop. After escaping on foot to the nearby apartment of his sister, Mixon shot and killed two police SWAT team officers attempting to apprehend him. Mixon was killed as other officers on the team returned fire.

This was the deadliest attack on California police officers since the Newhall massacre in 1970, when four California Highway Patrol officers were shot and killed by two men in Santa Clarita. It was also the deadliest attack on U.S. law enforcement since the September 11 attacks. The killing of four police officers in Lakewood, Washington, in November 2009 equaled it; and both were surpassed by a mass shooting in Dallas, Texas, in July 2016 that killed five police officers.