The Saint-Michel-de-Maurienne derailment of December 12, 1917 was a railway accident involving a troop train carrying at least 1,000 French soldiers on their way home for leave from the Italian front in World War I.

Following the Battle of Caporetto, which took place from October 24 to November 19 1917, a British and French Expeditionary Corps was sent to northeast Italy in order to reinforce the Italian front line.

On the night of December 12-13 1917, military train number 612 was returning from Italy filled with French soldiers who had spent a month helping Italian troops.

Due to a shortage of locomotives in the area, the local commanding officer for rail traffic chose to couple two trains with a combined 19 coaches to a single 4-6-0 engine.

The wooden coaches smashed into one another and promptly caught fire, caused by the overheated brakes and lit candles which had been brought aboard due to faulty electric lighting.

The derailment occurred at a point where the railway line passed through a narrow gap in the mountain terrain, leaving little room for heat from the fire to escape.

The locomotive driver (engineer) had been too preoccupied with his failing brakes and excessive speed to notice the absence of the cars until he reached the station at Saint Michel de Maurienne.

Together with some Scottish soldiers waiting to depart for Modane (two British divisions had also been sent to the Italian front in October) and railway employees from both stations, he went immediately to the accident site to assist.

Their task was made more difficult by the rocky terrain where the wrecked cars lay, by the heat from the fires, and by the height of the piled-up wreckage.

37 more bodies were found strewn along the ballast of the railway or the right-of-way, between La Praz and the metal bridge, belonging to soldiers who had jumped off the out-of-control train, or had been thrown off as it tossed wildly.

It also remains the second greatest rail catastrophe in the entirety of world history in terms of accurately known casualties, superseded only by the 2004 Sri Lanka tsunami train wreck.