900 mm gauge railways

narrow-gauge railways are generally found in Europe. This gauge is mostly used for light urban rail networks, industrial and agricultural railways.

Railways

Country/territory	Railway
Australia	Yallourn 900 mm railway
Austria	Linz urban tramways Florianerbahn Pöstlingbergbahn
Estonia	Vaivara–Viivikonna mine railway
Finland	Rokua railway
Georgia	Borjomi–Bakuriani railway "Kukushka" New Athos Cave Railway
Germany	Mecklenburgische Bäderbahn Dagebüll–Oland–Langeneß island railway Borkumer Kleinbahn, Isle of Borkum
Denmark	See Narrow-gauge railways in Denmark
Guernsey	1941–1946
Iceland	Reykjavík Harbour Railway
Indonesia	Used by Rendeng sugar mill for sugar cane transport
Ireland	Cork Electric Tramways and Lighting Company; opened 1898, closed 1931
Norway	Used by the Germans up to 1945, called Feldbahn, for industrial plants or other temporary uses. In Norway during the WW II the Germans built a railway between the harbour at Årdalstangen and the industrial plant of Øvre Årda. It closed in 1959, by then used only at the iron works. One steam locomotive was lost into the sea, but was found by divers around 1990 and is restored and exhibited at Aardalstangen.
Poland	Trams in Kraków
Portugal	Lisbon funiculars and tramways and their preceding mule cars Braga tramways Linha do Porto à Póvoa e Famalicão and its branch lines, built in 1871–1893 and regauged to in 1930
United States	Detroit Downtown Trolley

In Sweden, there was an extensive network of railways with track, some of them remain. This close enough to that they are more or less compatible, and some sales of rolling stock between the gauges have taken place.