Yūrakuchō Line

The line grew out of postwar subway planning. Urban Transportation Council Report No. 6 of 8 June 1962 set out a Line 10 of about 17.5 km from the Nakamurabashi area via Mejiro, Iidabashi and Asakusabashi to Kinshichō; on 29 August that year a Ministry of Construction notice re-designated this as Line 8. The route was substantially revised by Report No. 10 of 1968, which folded the Narimasu–Ikebukuro segment (formerly part of the Marunouchi Line) into Line 8, and again by Report No. 15 of 1 March 1972, which extended the southeastern end toward the bay and split a new Line 13 (Shiki–Mukaihara) off from the corridor. One purpose of the line was to relieve the crowded Marunouchi Line between Ikebukuro and Ginza, while also serving the developing wards of Itabashi, Nerima, Toshima and Kōtō.

The name was chosen by public competition: entries were taken from 1 November to 15 December 1973, drawing 30,591 submissions proposing 2,519 different names. The most popular vote-getter was "Kōjimachi Line," but because the kanji for "kōji" (麹) was not a general-use character at the time and was considered difficult and unfamiliar, and because many entries referred to Yūrakuchō — which would sit near the midpoint of the planned line — the name "Yūrakuchō Line" was decided on 9 January 1974. Other proposals included "Sakurada Line" and "Sotobori (Outer Moat) Line."

Construction of the first stretch, Ikebukuro–Ginza-itchōme, began on 19 August 1970, and the line opened for revenue service on 30 October 1974, run by the Teito Rapid Transit Authority (TRTA, or Eidan) with five-car Series 7000 trains. It was the eighth subway to open in Tokyo. The second section, Ginza-itchōme–Shintomichō, opened on 27 March 1980, and the third, Eidan-narimasu (now Chikatetsu-narimasu)–Ikebukuro, on 24 June 1983. Through service with the Seibu Yūrakuchō Line began on 1 October 1983 with the opening of the Kotake-mukaihara–Shin-Sakuradai segment.

The northwestern extension from Eidan-narimasu to Wakōshi opened on 25 August 1987, beginning through running with the Tōbu Tōjō Line. The final section, Shintomichō–Shin-Kiba, opened on 8 June 1988, completing the present line. On 7 December 1994 the "Yūrakuchō New Line" opened between Kotake-mukaihara and (Shin-line) Ikebukuro — physically the Line 13 tracks built alongside the Yūrakuchō Line — and full through running onward to the Seibu Ikebukuro Line via the Seibu Yūrakuchō Line began on 26 March 1998. During the Tokyo subway sarin attack of 20 March 1995, morning operations on the line were suspended and resumed in the afternoon.

On 1 April 2004 ownership passed from the Teito Rapid Transit Authority to Tokyo Metro Co., Ltd. on the former's privatisation, and the Eidan-narimasu and Eidan-akatsuka stations were renamed Chikatetsu-narimasu and Chikatetsu-akatsuka. Women-only cars were introduced on 31 October 2005, and the Series 10000 entered service on 1 September 2006. When the Tokyo Metro Fukutoshin Line opened on 14 June 2008, the Yūrakuchō New Line was absorbed into it, and the Wakōshi–Kotake-mukaihara section became track shared between the two lines. New CS-ATC signalling was rolled out section by section between 2002 and its completion on 4 August 2012, and automatic train operation (ATO) on all trains began on 22 May 2010.

Through the 2010s the line was fitted with platform screen doors at every station — completed in February 2014 — and the Series 17000 entered service on 21 February 2021. One-person ("wanman") operation, introduced on the Wakōshi–Kotake-mukaihara section in 2015, was extended to the Kotake-mukaihara–Shin-Kiba section on 6 August 2022. A branch from Toyosu Station northward to Sumiyoshi — about 4.8 km, long discussed since a 1972 council report originally proposed a longer Toyosu–Kameari line — received a Class 1 railway business licence on 28 March 2022; construction began on 5 November 2024, with opening targeted for the mid-2030s and through running planned via the Hanzōmon Line to Tōbu's Skytree, Isesaki and Nikkō lines.

• 19628 June: Urban Transportation Council Report No. 6 sets out a ~17.5 km Line 10 (Nakamurabashi–Kinshichō); on 29 August a Ministry of Construction notice re-designates it as Line 8.
• 1968Report No. 10 revises Line 8, folding the former Marunouchi Line section Narimasu–Ikebukuro into it; the route is set between Narimasu/Nerima and the Akashichō (now Shintomichō) area.
• 19721 March: Report No. 15 extends the southeastern end toward the bay and splits off a new Line 13 (Shiki–Mukaihara) from the corridor.
• 19749 January: the name 'Yūrakuchō Line' is decided (chosen from a public competition of 30,591 entries); 30 October: the first section, Ikebukuro–Ginza-itchōme, opens, run by the Teito Rapid Transit Authority with Series 7000 trains — the eighth subway to open in Tokyo.
• 198027 March: the second section, Ginza-itchōme–Shintomichō, opens.
• 198324 June: the third section, Eidan-narimasu (now Chikatetsu-narimasu)–Ikebukuro, opens. 1 October: through service with the Seibu Yūrakuchō Line begins with the opening of Kotake-mukaihara–Shin-Sakuradai.
• 198725 August: the northwestern extension Eidan-narimasu–Wakōshi opens, beginning through running with the Tōbu Tōjō Line.
• 19888 June: the final section, Shintomichō–Shin-Kiba, opens, completing the present Yūrakuchō Line.
• 19947 December: the 'Yūrakuchō New Line' (the Line 13 tracks, later the Fukutoshin Line) opens from Kotake-mukaihara to (Shin-line) Ikebukuro; through running reaches Nerima as the Seibu Yūrakuchō Line opens Shin-Sakuradai–Nerima.
• 199520 March: during the Tokyo subway sarin attack, morning operations on the line are suspended and resume in the afternoon.
• 199826 March: with the Seibu Yūrakuchō Line fully double-tracked, full through running to the Seibu Ikebukuro Line begins (extended as far as Hannō).
• 20041 April: ownership passes from the Teito Rapid Transit Authority (Eidan) to Tokyo Metro Co., Ltd. on the former's privatisation; Eidan-narimasu and Eidan-akatsuka are renamed Chikatetsu-narimasu and Chikatetsu-akatsuka.
• 20061 September: the Tokyo Metro 10000 series enters revenue service on the line.
• 200814 June: the Tokyo Metro Fukutoshin Line opens; the Yūrakuchō New Line is absorbed into it and the Wakōshi–Kotake-mukaihara section becomes track shared between the two lines.
• 20124 August: New CS-ATC signalling, rolled out section by section from 2002, is completed across the whole line (final section Shintomichō–Shin-Kiba).
• 202121 February: the Tokyo Metro 17000 series enters revenue service.
• 202228 March: a Class 1 railway business licence is granted for the ~4.8 km Toyosu–Sumiyoshi branch. 6 August: one-person ('wanman') operation begins on the Kotake-mukaihara–Shin-Kiba section.
• 20245 November: construction of the Toyosu–Sumiyoshi branch begins, with opening targeted for the mid-2030s.