Matsukawa derailment: Unknown saboteurs cause a passenger train to derail and overturn in Fukushima Prefecture, Japan, killing three crew members and igniting a political firestorm between the Japanese Communist Party and the government of Occupied Japan that will eventually lead to the Japanese Red Purge.

The Matsukawa derailment occurred at 03:09 AM on August 17, 1949 when a Tōhoku Main Line passenger train derailed and overturned between Kanayagawa and Matsukawa stations in Fukushima Prefecture of Japan, killing three crew members. Together with the Mitaka and Shimoyama incidents, it was one of three major criminal cases involving allegations of sabotage blamed by the government on the Japanese Communist Party and the Japan National Railway Union in the immediate post-war era. Twenty people were arrested and seventeen were convicted in 1953, but eventually all were acquitted on appeal, and the case was closed without determining the real cause in 1970.