The Nidareid train disaster was a train collision on 18 September 1921 on the Trondhjem-Størenbanen railway line, between the stations of Marienborg and Skansen in Trondheim, Norway. The accident occurred the day after the inauguration of the new line to Trondheim, Dovrebanen, and one of the trains involved was the inaugural train returning from the celebrations in Trondheim.