The Lagny-Pomponne Railroad Disaster was a train disaster that happened on December 23, 1933 between Pomponne and Lagny-sur-Marne (), twenty kilometers east of Paris, when the 4-8-2 locomotive of the express for Strasbourg crashed at 110 km the end of the extra train for Nancy which was stopped on the railway, destroying the five last wood cars. At this time of the year, both trains were full of people going to their families for Christmas. 204 people died and 120 were injured. It is the worst railroad disaster in French history after the Saint-Michel-de-Maurienne derailment disaster in 1917.