Meijō Line

The route was not built as a ring from the outset; it grew over nearly four decades out of two separate subway routes, Line 2 and Line 4, that were eventually joined end to end. The first section opened on 15 October 1965, when Line 2 began running the 1.3 km between Shiyakusho (City Hall, today Nagoyajō / Nagoya Castle) and Sakae-machi (today Sakae). At opening the line was worked by short 1000-series trains.

Line 2 was then extended in stages. On 30 March 1967 it reached south from Sakae to Kanayama, and on 25 April 1969 the route was given the name "Meijō Line." On 29 March 1971 the line was pushed further south from Kanayama to Nagoyakō (Port of Nagoya), and on 20 December 1971 the northern end was completed between Ōzone and Shiyakusho, finishing Line 2 as a through route from Ōzone in the north down to the port.

The second component, Line 4, opened its first section on 30 March 1974, running 5.7 km between Aratama-bashi (Shin-Mizuhashi) and Kanayama. For the next three decades the two lines operated as distinct services while the network around them grew; a new station, Hisaya-ōdōri, was inserted between Shiyakusho and Sakae on 10 September 1989, the same day the Sakura-dōri Line opened, and the original 1000-series cars were retired by 2000 in favour of the 2000 series introduced in 1989.

Line 4 was extended around the eastern side of the city in a series of openings: Ōzone to Sunadabashi on 19 January 2000, Sunadabashi to Nagoya University on 13 December 2003, and finally Nagoya University to Aratama-bashi (Shin-Mizuhashi) on 6 October 2004. That last 5.6 km segment closed the gap between the two routes. On the same day the combined ring of Line 2 and Line 4 was designated the Meijō Line, and the remaining stretch from Kanayama out to Nagoyakō — now hanging off the loop as a branch — was renamed the Meikō Line (名港線). With the ring complete, Japan's first subway loop operation began, with trains running continuously around the circle and through services linking the loop to the Meikō branch at Kanayama.

Since the loop opened, the line has been steadily modernised. Women-only cars were introduced on weekday mornings from 4 July 2016, and platform-edge gates were progressively installed, first entering service at Kanayama in July 2020 and reaching every station by 15 March 2021. Automatic train operation began with the 23 May 2020 timetable revision, which also lengthened a full circuit of the loop to about 60 minutes, and driver-only (one-person) operation was extended to the whole line by 1 July 2022. On 4 January 2023 three stations were renamed — Shiyakusho to Nagoyajō (Nagoya Castle), and the Atsuta-area stations Denma-chō and Jingū-nishi gaining "Atsuta Jingū" prefixes — reflecting the landmarks they serve.

Today the Meijō Line is one of the busiest routes of the Nagoya subway, valued both as a continuous circular connector tying together the city's commercial, civic and university districts and as an interchange with the radial lines that cross it. Its status as the country's first and only genuine subway loop remains its defining distinction.

• 196515 October: Line 2 opens its first section, Shiyakusho (now Nagoyajō / Nagoya Castle)–Sakae-machi (now Sakae), 1.3 km, worked by 1000-series trains.
• 196730 March: Line 2 is extended south from Sakae to Kanayama, 3.0 km.
• 196925 April: Line 2 is given the nickname 'Meijō Line'.
• 197129 March: Kanayama–Nagoyakō (Port of Nagoya) opens, 6.0 km; 20 December: Ōzone–Shiyakusho opens, completing Line 2 as a through route.
• 197430 March: Line 4 opens its first section, Aratama-bashi (Shin-Mizuhashi)–Kanayama, 5.7 km.
• 198910 September: Hisaya-ōdōri Station opens between Shiyakusho and Sakae, the same day as the Sakura-dōri Line; the 2000-series trains had entered service on 10 June.
• 200019 January: Line 4 is extended Ōzone–Sunadabashi, 1.7 km; 31 March: the 1000-series trains end revenue service.
• 200313 December: Line 4 is extended Sunadabashi–Nagoya University, 4.5 km.
• 20046 October: the final Nagoya University–Aratama-bashi segment (5.6 km) opens, closing the ring; the combined Line 2 + Line 4 loop is designated the Meijō Line and the Kanayama–Nagoyakō branch is renamed the Meikō Line. Japan's first subway loop operation begins.
• 20164 July: women-only cars are introduced on weekday mornings until 9 a.m.
• 202023 May: a timetable revision lengthens one loop to about 60 minutes and automatic train operation (ATO) begins; platform-edge gates start installation from 25 May.
• 202115 March: platform-edge gates become operational at all stations (first having entered service at Kanayama in July 2020); 1 July: one-person operation begins on the Nagoya Dome-mae Yada–Motoyama–Kanayama section.
• 20221 July: one-person (driver-only) operation is extended to the whole line.
• 20234 January: three stations are renamed — Shiyakusho to Nagoyajō (Nagoya Castle), and the Denma-chō and Jingū-nishi stations gain 'Atsuta Jingū' prefixes.