The Urskog–Høland Line (Norwegian: Urskog–Hølandsbanen), also known as Tertitten, is a narrow gauge railway between Sørumsand and Skulerud in Norway. The original line was 57 kilometres (35 mi) long and was built in three stages: Urskogbanen opened in 1896, running from Bingsfossen to Bjørkelangen; Hølandsbanen from Bjørkelangen to Skulerud opened in 1898 and finally the line between Bingsfos and Sørumsand in 1903. Today part of the line is preserved as a museum at Sørumsand in Sørum kommune. The railway company was headquartered at Bjørkelangen. The line was built in the least expensive way as a so-called tertiary railway with a 750 mm (2 ft 5 1⁄2 in) gauge track. This gave the line its diminutive, affectionate nickname, "Tertitten". The railway was run as a privately owned joint stock company until 1945 when it was bought by the government and run by the Norwegian State Railways (NSB) under the name Aurskog-Hølandbanen.
The basis for the railway lay mostly in forest and agriculture products. Lumber was transported to Skulreud and from there it was rafted to Halden. At one time a tour billed as "The Great Roundtrip" was a popular tourist attraction, combining the train ride with a boat ride on the steam ship "DS Turisten" which trafficked the Halden Canal.
A cooperative consisting of volunteers was established in 1961 with the aim of securing the line for posterity. A 3-kilometer track at Sørumsand was given to the group along with two steam locomotives and some other stock. The first run as a heritage railway was undertaken in 1966. This stretch had no buildings or side tracks, and all facilities which meet the present-day visitor was built after becoming a heritage railway. Three of the steam locomotives and two passenger carriages were restored.
When the heritage railway was established the terminus was just outside the town center of Sørumsand, with the track leading to the station building already having been removed. In 1987 the line had been extended and the first train could depart from the town center again. After another two years the entire operation, including station building, was finished, and the extended track was officially inaugurated. The entire complex is protected by law. The Urskog–Høland Line is now a foundation, "Venneforeningen Tertitten".