Токио метросының Шығыс-Батыс желісі

Subway line in Tokyo, Japan

The Tokyo Metro Tozai Line (東京メトロ東西線) is a rapid transit line in Tokyo and Chiba Prefecture, Japan, owned and operated by Tokyo Metro. Its name translates to "East West Line". The line runs between Nakano in Nakano ku, Tokyo and Nishi Funabashi in Funabashi, Chiba Prefecture. The Tōzai Line was referred to as Line 5 during the planning stages; the seldom used official name is Line 5 Tōzai Line (5号線東西線). The line carries an average of 1,642,378 passengers daily (2017), making it the busiest line on the Tokyo Metro network. Women only cars were introduced on the line for use during morning rush hour on November 20, 2006. During the COVID 19 pandemic, peak ridership dropped from a rate of 199% in 2019 to 123% in 2020.

The Tōzai Line was planned by a review committee of the then Ministry of Transportation in 1962 and numbered Line 5. Its name literally means "East West Line", and it was primarily planned to relieve traffic on the busy Sōbu Main Line as well as provide a straight crosstown connection through north central Tokyo. Although this corridor is also served by the Tokyo Metropolitan Bureau of Transportation (Toei) Shinjuku Line and JR Keiyō Line, the Tōzai Line continues to operate beyond capacity due to its accessibility to other lines, as well as to growing condominium developments in eastern Tokyo. The to section opened in 1964, and the remainder opened in stages until its completion in 1969. Through service with the then Japanese National Railways (today part of the JR Group) – a first for a Tokyo subway line – began in 1969 connecting the Chūō and Sōbu lines. This is a rare situation in Tokyo, as the only other subway line with through services onto JR lines is the Chiyoda Line. The Tōyō Rapid Railway Line, effectively an eastward extension of the line, opened in 1996. It nevertheless remains a private entity to which the Tōzai lines offers through services.

March 16, 1966: The line is extended at both ends. It now runs between Nakano and Takebashi. April 28, 1966: Through service to the Chūō Line of JNR commences as far as Ogikubo. October 1, 1966: Takebashi to Ōtemachi section opens. September 14, 1967: Ōtemachi to Tōyōchō section opens. March 29, 1969: Tōyōchō to Nishi Funabashi section opens and Rapid service begins (non stop between Tōyōchō and Nishi Funabashi). April 8, 1969: Through service on the Chūō Line is extended to Mitaka, and through service begins on the Sōbu line to Tsudanuma. April 8, 1972: Through service on the Sōbu Line is withdrawn except during rush hours. 1975: Another type of Rapid service is introduced, calling at Urayasu between Tōyōchō and Nishi Funabashi. October 1, 1979: Nishi Kasai station opens. March 27, 1981: Minami Gyōtoku station opens. 1986: Commuter Rapid service is introduced, running non stop between Urayasu and Nishi Funabashi. (April 1, 1987: JNR is privatised. The Chūō and Sōbu lines become the property of JR East.) 1996: The Rapid service that runs non stop between Tōyōchō and Nishi Funabashi ceases. April 27, 1996: Tōyō Rapid Line opens between Nishi Funabashi and Tōyō Katsutadai. Through service begins. January 22, 2000: Myōden station opens. April 1, 2004: Teito Rapid Transit Authority (TRTA or Eidan) becomes Tokyo Metro. November 20, 2006: Women only cars are introduced during morning rush hours.

The Tōzai Line was the first Tokyo Metro line on which express services run: two types of rapid trains skip some stations east of Toyocho. The Tokyo Metro Fukutoshin Line began services on June 14, 2008, and also features express services. Through services to via the JR East Chūō Line and via the Tōyō Rapid Railway run all day. During the morning and evening peak periods, through services run to via the JR East Sōbu Line.