The Tokyo Subway (地下鉄 chikatetsu) system is one of the world's most extensive metro/subway networks. There are two primary metro/subway systems in Tokyo, which are operated by

• Tokyo Metro Co. Ltd (formerly Teito Rapid Transit Authority [Eidan]), 8 lines. The lines are called Tokyo Metro in English. Minimum price for one ride: 160 yen.
• Tokyo Metropolitan Bureau of Transportation (Toei), 4 lines. The lines are called Toei Subway in English. Minimum price for one ride: 170 yen.

Several other railways in the capital, notably the Tokyo Waterfront Railway, also qualify as metro (subway) by most definitions.

On April 1, 2004, the Teito Rapid Transit Authority (TRTA) was privatized and renamed the Tokyo Metro Co. Ltd (東京地下鉄株式会社, Tōkyō Chikatetsu K.K.). The company also uses the name Tokyo Metro (東京メトロ) in Japanese for promotional purposes.

The privatization affected only the TRTA, and the Tokyo Metropolitan Government continues to operate its own Toei lines separately.

The separate administration of two metro systems in the same city causes several annoyances for customers:

• Double ticketing: The two systems cannot be used with the same ticket. An additional 90 or 100 yen is charged if one switches to a line in the other system regardless how short the whole ride might be.
• Both systems represent the metro network with different maps in stations, trains or customer information brochures. The schematisms used to represent the line network focus on the system's respective own lines, making orientation difficult when changing the system. For example, in the Toei maps, the Toei Oedo Line is represented as a circle in the centre, implying a key function for Tokyo's whole public transport system, while in Tokyo Metro's map, the Oedo Line follows more its natural rectangular layout. Here, the centre line is the JR Yamanote Line.