The Setesdal Line was a railway between Kristiansand and Byglandsfjord in southern Norway, 78 km (48 mi) long. It was built with a narrow gauge of 1,067 mm, and opened to Hægeland 26 November 1895, and to Byglandsfjord 27 November 1896. Stations along the line included Mosby, Vennesla, Grovene (Grovane), Iveland and Hægeland.

Railways with a track gauge of 3 ft 6 in were first constructed as horse-drawn wagonways. The first intercity passenger railway to use 3 ft 6 in was constructed in Norway by Carl Abraham Pihl. From the mid-nineteenth century, the 3 ft 6 in gauge became widespread in the British Empire. In Africa it became known as the Cape gauge as it was adopted as the standard gauge for the Cape Government Railways in 1873, although it had already been established in Australia and New Zealand before that. It was adopted as a standard in New Zealand, South Africa, Indonesia, Japan, the Philippines, Taiwan, and Queensland in Australia.