The Little Saw Mill Run Railroad was a 4 ft 8 1⁄2 in standard gauge coal railroad in Allegheny County, Pennsylvania. It was incorporated July 23, 1850, and opened in April 1853. Originally, it was owned by the Harmony Society, and ran from Temperanceville, Pennsylvania on the Ohio River to Banksville, Pennsylvania, running parallel to Saw Mill Run and Little Saw Mill Run. In an agreement with the 3 ft narrow gauge Pittsburgh Southern Railroad, it ran dual gauge tracks. It became part of the railroad empire of George J. Gould, merging with the West Side Belt Railroad in 1897.