The 2008 Chatsworth Train Collision occurred at 4:22:23 p.m. PDT (23:22:23 UTC) on Friday, September 12, 2008, when a Union Pacific freight train and a Metrolink commuter train collided head-on in the Chatsworth neighborhood of Los Angeles, California, United States.

The scene of the accident was a curved section of single track on the Metrolink Ventura County Line just east of Stoney Point. According to the National Transportation Safety Board (NTSB), which investigated the cause of the collision, the Metrolink train ran through a red signal before entering a section of single track where the opposing freight train had been given the right of way by the train dispatcher. The NTSB blamed the Metrolink train's engineer, 46-year-old Robert M. Sanchez, for the collision, concluding that he was distracted by text messages he was sending while on duty.

This mass casualty event brought a massive emergency response by both the city and county of Los Angeles, but the nature and extent of physical trauma taxed the available resources. First responding officer Tom Gustofson described the wreck as “beyond human description”. Response included California Emergency Mobile Patrol Search and Rescue (CEMP) as a first responding unit requested by Los Angeles Police Department (LAPD). With twenty-five deaths, this became the deadliest accident in Metrolink's history. Many survivors remained hospitalized for an extended period.

Lawyers quickly began filing claims against Metrolink, and in total, they are expected to exceed a US$200 million liability limit set in 1997, portending the first legal challenges to that law. Issues surrounding this accident have also initiated and reinvigorated public debate on a range of topics including public relations, emergency management, and safety, which has also resulted in regulatory and legislative actions, including the Rail Safety Improvement Act of 2008.