The Interurban (or radial railway in Europe and Canada) is a type of electric railway, with streetcar-like electric self-propelled rail cars which run within and between cities or towns. They were very prevalent in North America between 1900 and 1925 and were used primarily for passenger travel between cities and their surrounding suburban and rural communities. The concept spread to countries such as Japan, the Netherlands, Switzerland, Belgium, Italy and Poland. Interurban as a term encompassed the companies, their infrastructure, their cars that ran on the rails, and their service. In the United States, the early 1900s interurban was a valuable economic institution. Most roads between towns and many town streets were unpaved. Transportation and haulage was by horse-drawn carriages and carts. The interurban provided reliable transportation, particularly in winter weather, between the town and countryside. In 1915, 15,500 miles (24,900 km) of interurban railways were operating in the United States and, for a few years, interurban railways, including the numerous manufacturers of cars and equipment, were the fifth-largest industry in the country. By 1930, most interurbans in North America were gone with a few surviving into the 1950s.

Outside of the US large networks of high-speed electric tramways have been built in countries across the world that survive today. Notable systems exist in the Low Countries, Poland and Japan, where populations are densely packed around large conurbations such as the Randstad, Upper Silesia, Greater Tokyo Area and Keihanshin. Switzerland, particularly, has a large network of mountain narrow gauge interurban lines.

In addition, many tram-train lines are being built, especially in France and Germany but also elsewhere in the world. These can be regarded as interurbans since they run on the streets, like trams, when in cities, while out of them they either share existing railway lines or put lines abandoned by the railway companies to a new use.