Namboku Line

The line through-runs onto adjoining railways at both ends. In the south, trains continue over the Tōkyū Meguro Line toward Hiyoshi, and from there onto the Tōkyū Shin-Yokohama Line and the Sagami Railway. In the north, services run through onto the Saitama Rapid Railway Line toward Urawa-Misono, a line that functions essentially as a separately owned extension of the Namboku Line. Between Shirokane-Takanawa and Meguro the right-of-way and stations are shared with the Toei Mita Line, an arrangement unique on the Tokyo subway in which two operators share common infrastructure.

The route has its origins in the early 1960s. In June 1962 the Tokyo Urban Transportation Council's Report No. 6 set out Line 7 as a route from the Meguro direction via Iikura-katamachi, Nagatachō, Ichigaya, Komagome and Ōji toward Akabane, and on 29 August 1962 it was formally fixed as City Planning Line 7. The Teito Rapid Transit Authority (TRTA, the forerunner of Tokyo Metro) applied for a construction licence that October, but planning then stalled for years, chiefly over opposition to a planned depot in Kita Ward. The full-route licence, for Meguro to Iwabuchi-chō, was finally granted on 20 April 1984 — twenty-two years after the original application.

Construction of the first section, from Komagome to Iwabuchi-chō, began on 1 February 1986. The first segment of the line, from Komagome to Akabane-Iwabuchi (6.3 km), opened on 29 November 1991, worked by 9000 series trains in four-car formations. The name "Namboku Line" had been chosen through a staff competition and announced earlier that year, the geographic sense of a line running north–south through Tokyo making it the natural counterpart to the existing Tōzai (East–West) Line.

The line was then extended south in stages, with construction repeatedly delayed by archaeological excavation of Edo-period remains between Tameike-Sannō and Iidabashi and by local opposition near Shirokanedai. Six-car operation began in February 1996, and on 26 March 1996 the line was extended from Yotsuya to Komagome (7.1 km). The Tameike-Sannō to Yotsuya section (2.2 km) opened on 30 September 1997.

The final stretch, from Meguro to Tameike-Sannō (5.7 km), opened on 26 September 2000, completing the line and simultaneously inaugurating through service onto the Tōkyū Meguro Line toward Musashi-Kosugi. Through service with the newly opened Saitama Rapid Railway Line began on 28 March 2001, extending trains north toward Urawa-Misono and later carrying traffic to Saitama Stadium for the 2002 FIFA World Cup. On 1 April 2004 the Namboku Line passed to the newly created Tokyo Metro on the privatisation of the TRTA, and in June 2008 the southern through service was extended to Hiyoshi as the Tōkyū Meguro Line itself was lengthened.

More recently the line's capacity has been expanded and its network reach widened. Eight-car operation began on 1 April 2022, supported by platform extensions completed across many stations. On 18 March 2023 a major reorganisation brought new through services via the Tōkyū Shin-Yokohama Line onto the Sagami Railway, with many southbound trains running as far as Shin-Yokohama and Ebina. A 2.5-kilometre branch from Shirokane-Takanawa to Shinagawa has also been authorised, with construction begun in November 2024, intended to improve connections to the planned Chūō Shinkansen at Shinagawa.

• 19628 June: the Tokyo Urban Transportation Council's Report No. 6 designates Line 7; on 29 August it is formally fixed as City Planning Line 7. On 16 October the TRTA applies for a construction licence (Meguro–Akabane-chō, ~22.5 km).
• 19644 June: the Tokyo Metropolitan Government also applies for a Line 7 licence (Meguro–Akabane, ~21.0 km), creating competing applications; the TMG application is later withdrawn on 23 October 1972.
• 198420 April: the full-route licence, Meguro to Iwabuchi-chō, is granted — twenty-two years after the original application, the delay caused chiefly by opposition to a planned depot in Kita Ward.
• 19861 February: construction of the first section, Komagome to Iwabuchi-chō, begins (authorised 21 January).
• 199129 November: the first segment, Komagome–Akabane-Iwabuchi (6.3 km), opens, worked by 9000 series trains in four-car formations. The name 'Namboku Line', chosen by staff competition, had been announced on 27 June.
• 19963 February: six-car operation begins. 26 March: the line is extended from Yotsuya to Komagome (7.1 km).
• 199730 September: the Tameike-Sannō–Yotsuya section (2.2 km) opens.
• 200026 September: the final stretch, Meguro–Tameike-Sannō (5.7 km), opens, completing the line; through service onto the Tōkyū Meguro Line toward Musashi-Kosugi begins the same day.
• 200128 March: through service with the newly opened Saitama Rapid Railway Line begins, extending trains north toward Urawa-Misono; the link later carried traffic to Saitama Stadium for the 2002 FIFA World Cup.
• 20041 April: on the privatisation of the Teito Rapid Transit Authority, the Namboku Line is inherited by the newly created Tokyo Metro.
• 200822 June: with the Tōkyū Meguro Line extended from Musashi-Kosugi to Hiyoshi, the southern through service is extended to Hiyoshi.
• 20221 April: eight-car operation begins, supported by platform extensions across many stations.
• 202318 March: a major service reorganisation brings new through running via the Tōkyū Shin-Yokohama Line onto the Sagami Railway, with many southbound trains reaching Shin-Yokohama and Ebina.
• 20245 November: construction begins on the authorised 2.5 km branch from Shirokane-Takanawa to Shinagawa, intended to improve connections to the planned Chūō Shinkansen at Shinagawa.