Note: This article only lists tunnels that are 15 km (6.2 miles) or longer.
| width=220pt | Name | width=220pt | System | Country | Stations | Length in km (mi) | Year of
completion< | -- Don't add Hong Kong MTR's West Rail line, since a large part of it is above ground. There is also a short submerged but uncovered stretch to the north of Hunghom station, and an overground but covered stretch to the west of Nam Cheong station. --> |
|---|
| Lines 3-11 | Suzhou Metro |  China | Line 3 and Line 11 are connected at Weiting Station with through trains passing by. | 86.54km (53.77miles) | 2019–2023 |
| Line 6 | Chengdu Metro | China | Wangcong Temple – Lanjiagou | 68.2 (42.4)[1] | 2020 |
| Line 19 | Chengdu Metro | China | Huangshi to Tianfu | 67km (42miles) | 2020–2023 |
| Line 1 | Qingdao Metro | China | Dongguozhuang to Wangjiagang | 59.82km (37.17miles) | 2020–2021 |
| Line 18 | Guangzhou Metro | China | to | 58.3 (36.2)[2] | 2021 |
| Line 3 | Guangzhou Metro | China | Airport North – Panyu Square | 57.93 (36) | 2005–2018 |
| Bolshaya Koltsevaya line | Moscow Metro | | Circle route | 57.54km (35.75miles)[3] [4]
(excluding Moscow-City branch) | 2018–2023[5] |
| Line 10 | Beijing Subway | China | Circle route | 57.1 (35.5) | 2008–2013 |
| Line 6 | Beijing Subway | China | – | 53.4 (33.2) | 2012–2018 |
Seoul Subway Line 5
(longest branch) | Seoul Subway | | Banghwa–Hanam Geomdansan | 51.7km (32.1miles) | 1995–2021 |
| M11 | Istanbul Metro |  Turkey | Gayrettepe – Arnavutköy Hastane | 51.5 (32) | 2023–2024 |
| Line 2 | Wuhan Metro | China | Julong Boulevard - Fozuling | 50.347 (27.556) | 2012–2019 |
| Arbatsko-Pokrovskaya line | Moscow Metro | | Pyatnitskoye Shosse – Shchyolkovskaya | 45.1 (28.0) | 1938–2012 |
| Sokolnicheskaya line | Moscow Metro | | Kommunarka – Bulvar Rokossovskogo | 44.5 (27.7) | 1935–2019 |
| Lyublinsko-Dmitrovskaya line | Moscow Metro | | Zyablikovo – Fiztekh | 44.3 (27.5) | 1995–2023 |
| Zamoskvoretskaya line | Moscow Metro | | Khovrino – Alma-Atinskaya | 42.8 (26.6) | 1938–2018 |
| Line 8 | Beijing Subway | China | – | 42.6 (26.4) | 2012–2021 |
| Line 15 | Shanghai Metro | China | Gucun Park – Zizhu Hi-tech Park | 42.3 (26.3) | 2021 |
| Line 5 | Chengdu Metro | China | Jiudaoyan – Huilong | 42.3 (26.3) | 2019 |
| Tagansko-Krasnopresnenskaya line | Moscow Metro | | Planernaya – Kotelniki | 42.2 (26.2) | 1966–2015 |
| Line 14 | Beijing Subway | China | – | 42 (26) | 2015–2021 |
| Line 6 | Tianjin Metro | China | – | 42 (26) | 2016–2021 |
| Downtown MRT line | Mass Rapid Transit (Singapore) |  Singapore | Bukit Panjang – Expo | 41.9 (26)[6] | 2013–2017 |
| Line 3 | Nanjing Metro | China | Xinghuolu – Mozhoudonglu | 41.5 (25.8) | 2015 |
| Line 4 | Suzhou Metro | China | Longdaobang — Tongli | 41.5 (25.8) | 2017 |
| Serpukhovsko-Timiryazevskaya line | Moscow Metro | | Altufyevo – Bulvar Dmitriya Donskogo | 41.2 (25.6) | 1983–2002 |
| L-12 (Metro Sur) | Madrid Metro |  Spain | Circle route | 40.96 (25.5) | 2003 |
| Toei Subway |  Japan | Hikarigaoka – Shiodome – Tocho-mae | 40.7 (25.3) | 2000 |
| Seoul Subway Line 9 | Seoul Subway | | Gimpo Airport – VHS Medical Center | 40.6 (25.2) | 2018 |
| Line 12 | Shanghai Metro | China | Qixin Road – Jinhai Road | 40.4 (25.1) | 2015 |
| Line 7 | Beijing Subway | China | - | 40.3 (25.0) | 2021 |
| Line 4 | Chengdu Metro | China | Wansheng – Chengdu University | 39.3 (24.4) | 2015–2017 |
| Line 7 | Chengdu Metro | China | Circle route | 38.6 (24.0) | 2017 |
| Line 3 | Chengdu Metro | China | Chengdu Junqu General Hospital – Shuangliu West Station | 38.1 (23.7) | 2018 --> |
|---|
| Kaluzhsko-Rizhskaya line | Moscow Metro | | Medvedkovo – Novoyasenevskaya | 37.8 (23.5) | 1958–1990 |
| Line 1 | Chengdu Metro | China | Weijianian – Science City | 37.47 (23.3) | 2010–2018 |
| Line 2 | Shenzhen Metro | China | Chiwan – Xinxiu | 35.78 (22.23) | 2011 |
| Busan Subway Line 2 | Busan Transportation Corporation | | Jangsan–Dongwon | 35.5 (22.06) | 1999 |
| Seoul Subway Line 6 | Seoul Subway | | Eungam Loop – Bonghwasan | 35.1 (21.8) | 2001 |
Seoul Subway Line 7
(longest branch) | Seoul Subway | | Cheongdam – Bupyeong-gu Office | 35.1 (21.7) | 2012 |
| Line 5 | Tianjin Metro | China | – | 34.8 (21.6) | 2018–2021 |
| Line 7 | Shanghai Metro | China | Panguang Road – Huamu Road | 34.4 (21.38) | 2010 |
| Line 8 | Guangzhou Metro | China | Wanshengwei—Jiaoxin | 33.9 (21.1) | 2010–2020 |
| M4 | Istanbul Metro | Turkey | Kadıköy – Sabiha Gökçen Havalimanı | 33.5 (20.8) | 2012–2022 |
| Circle MRT line | Mass Rapid Transit (Singapore) | Singapore | Dhoby Ghaut – HarbourFront | 33.3 (20.69)[7] | 2009–2012 |
| L-7 | Madrid Metro | Spain | Hospital del Henares – Pitis | 32.9 (20.5) | 2007 |
| U7 | Berlin U-Bahn |  Germany | Rathaus Spandau-Rudow | 31.8 (19.7)[8] | 1924–1984 |
| Line 1 | Beijing Subway | China | – | 31.0 (19.3) | 1971–2000 |
| Line 16 | Beijing Subway | China | – | 31.0 (19.2) | 2016–2021 |
| Solntsevskaya line | Moscow Metro | | Aeroport Vnukovo – Delovoy Tsentr | 30.9 (19.2) | 2014–2023 |
| IND Eighth Avenue Line and IND Fulton Street Line[9] | New York City Subway |  United States | Inwood – 207th Street – Grant Avenue | 30.8 (19.14) | 1956 |
| Line 2 Orange | Montreal Metro |  Canada | Côte-Vertu – Montmorency | 30.8 (19.14) | 2007 |
| Thomson–East Coast line | Mass Rapid Transit (Singapore) | Singapore | Woodlands North – Gardens by the Bay | 30.4km (18.9miles) | 2020–2022 |
| Line 2 | Shanghai Metro | China | East Xujing – Longyang Road | 30.2 (18.77) | 2010 |
| Moskovsko-Petrogradskaya Line | Saint Petersburg Metro | | Parnas–Kupchino | 30.1 (18.7) | 1961–2006 |
| Line 8 | Shanghai Metro | China | Shiguang Road – Luheng Road | 29.7 (18.45) | 2009 |
| Kirovsko-Vyborgskaya Line | Saint Petersburg Metro | | Devyatkino – Prospekt Veteranov | 29.57 (18.4) | 1955–1978 |
| Line 8 | Chengdu Metro | China | (Phase 2 is 7.94 km) | 29.1 (18.1) | 2020 |
| Line 2 | Chengdu Metro | China | Tianhe Road – Chengdu Institute of Public Administration | 29.0 (18.0) | 2012–2013 |
| Bannan Line (Taipei Metro Blue Line) | Taipei Metro | | Dingpu – Taipei Nangang Exhibition Center | 28.2 (17.6)
| 1999–2015 |
| Line 4 | Beijing Subway | China | – | 28.2 (17.5) | 2009–2010 |
| Incheon Subway Line 1 | Incheon Subway | | Bakchon – International Business District | 27.9 (17.42) | 1999–2009 |
| Northern line | London Underground |  United Kingdom | Morden – East Finchley | 27.8 (17.2) | 1890–1940 |
| Nevsko-Vasileostrovskaya Line | Saint Petersburg Metro | | Begovaya–Rybatskoye | 27.7 (17.2) | 1967–2018 |
| Tanimachi Line | Osaka Metro | Japan | Dainichi–Nagahara | 27.1 (16.7) | 1967–1983 |
| M5 | Istanbul Metro | Turkey | Üsküdar – Samandıra Merkez | 26.5 (12.5) | 2017–2024 |
| Nagoya Municipal Subway | Japan | Kanayama–Nagoya Dome-mae Yada-Kanayama | 26.4 (16.4) | 1965–2004 |
| B Line | Los Angeles Metro Rail | United States | - | 26.4 (16.4) | 1993–2000 |
| Frunzensko-Primorskaya Line | Saint Petersburg Metro | | Komendantsky Prospekt – Shushary | 26.2 (16.3) | 1997–2019 |
| Line 1 | Suzhou Metro | China | Mudu – Zhongnan Jie | 25.7 (16.0) | 2012 |
| Line 3 | Athens Metro |  Greece | – Doukissis Plakentias | 25.3 (15.72) | 2023 |
| Helsinki Metro | Helsinki Metro |  Finland | Kalasatama – Kivenlahti | 25.2 (15.7) | 1982–2022 |
| Orange Line | Taipei Metro | | Huilong–Nanshijiao | 25.1 (15.6)
(longest branch) | 1998–2013 |
| Line 3 | Santiago Metro |  Chile | Plaza de Quilicura - Fernando Castillo Velasco | 25 (13.5) | 2019–2023 |
| Yurakucho Line | Tokyo Metro | Japan | Chikatetsu Narimasu – Tatsumi | 24.6 (15.3) | 1974–1988 |
| U2 | Munich U-Bahn | Germany | Feldmoching – Messestadt Ost | 24.4 (15.2) | 1980–2001 |
| Yellow Line | Delhi Metro |  India | GTB Nagar – Saket | 24 (14.9)[10] [11] | 2009–2010 |
| L-1 | Madrid Metro | Spain | Valdecarros – Pinar de Chamartín | 23.88 (14.84) | 1919–2007 |
| L-6 | Madrid Metro | Spain | Circle route | 23.47 (14.58) | 1979–2007 |
| Line 9 | Shanghai Metro | China | Jiuting – Middle Yanggao Road | 23.3 (14.48) | 2007–2010 |
| Line 1 Green | Montreal Metro | Canada | Angrignon – Honoré-Beaugrand | 23.26 (14.45) | 1966–1978 |
| Warsaw Metro M1 | Warsaw Metro |  Poland | Kabaty–Młociny | 23.1 (14.35) | 1995–2008 |
| Line 2 | Beijing Subway | China | Circle route | 23.1 (14.35) | 1984–1987 |
| M3 | Istanbul Metro | Turkey | Bakırköy Sahil – Şehir Hastanesi Viaduct | 22.6 (16.6) | 2013–2024 |
| Line 9 | Chengdu Metro | China | Phase 1 of the second loop line in Chengdu, all underground | 22.18km (13.78miles) | 2020 |
| Line 19 | Beijing Subway | China | – | 22.4 (13.9) | 2021 |
| Songshan-Xindian Line (Taipei Metro Green Line) | Taipei Metro | | Songshan-Xindian | 21.3 (13.2) | 1998–2014 |
| Line 4 | Shanghai Metro | China | Hailun Road – Yishan Road | 21.1 (13.11) | 2005–2007 |
| Toei Mita Line | Toei Subway | Japan | Meguro – Shimura-Sakaue | 21.1 (13.11) | 1968–2000 |
| Victoria line | London Underground | United Kingdom | Walthamstow Central – Brixton | 21.0 (13.05) | 1968–1971 |
| Obolonsko–Teremkivska line | Kyiv Metro |  Ukraine | Heroiv Dnipra–Teremky | 20.95 (13.02) | 1976–2013 |
| Line 6 | Shanghai Metro | China | Boxing Road – Oriental Sports Center | 20.34 (12.64) | 2007–2011 |
| Line 1 | Barcelona Metro | Spain | Fondo – Hospital de Bellvitge | 20.2 (12.56) | 1926–1989 |
| | Japan | Miyanosawa – Shin-Sapporo | 20.1 (12.4) | 1976–1999 |
| M1 | Ankara Metro | Turkey | Koru – Atatürk Kültür Merkezi | 20.1 (12.4) | 1997–2014 |
| L-5 | Madrid Metro | Spain | Alameda de Osuna – Empalme | 20.005 (12.5) | 1968–2006 |
| Line 9 | Barcelona Metro | Spain | Zona Universitaria – Aeroport T1 | 20.0 (12.5) | 2004–2016 |
| North East MRT line | Mass Rapid Transit (Singapore) | Singapore | HarbourFront–Punggol | 20.0 (12.43)[12] | 2003–2011 |
| Bucharest Metro Line M3 | Bucharest Metro |  Romania | Preciziei – Anghel Saligny | 20.0 (12.43) | 1983–2008 |
| Line 2 | Tianjin Metro | China | – | 19.7 (12.2) | 2012–2014 |
| Nekrasovskaya line | Moscow Metro | | Nizhegorodskaya – Nekrasovka | 19.6 (12.2) | 2019–2020 |
| Paris Métro Line 9 | Paris Métro |  France | Pont de Sèvres – Mairie de Montreuil | 19.6 (12.18) | 1922–1937 |
| M2 | Istanbul Metro | Turkey | Şişhane – Hacıosman
Line is 23,49 km long, but the longest continuous underground section is 19.54 km long. | 19.54 (12.14) | 2000–2014 |
| Red, Yellow, Blue, and Green Lines | Bay Area Rapid Transit, San Francisco | United States | – | 19.5 (12.12) | 1973 |
| Metro Northwest | Sydney Metro |  Australia | Cherrybrook–Chatswood | | 2009–2019 |
| Kol'tsevaya Line | Moscow Metro | | Circle route | 19.4 (12.2) | 1950–1954 |
| U3 | Munich U-Bahn | Germany | Moosach – Fürstenried West | 19.4 (12.05) | 1972–2009 |
| Line 4 | Tianjin Metro | China | – | 19.4 (12) | 2021 |
| Line 3 | Tianjin Metro | China | – | 19.2 (11.9) | 2012–2013 |
| Maskoŭskaja line | Minsk Metro |  Belarus | Malinawka–Uruchcha | 19.1 (11.9) | 1984–2014 |
| Midosuji Line | Osaka Metro | Japan | Nakatsu – Nakamozu | 19.1 (11.87) | 1933–1987 |
| Line 5 | Barcelona Metro | Spain | Vall d'Hebron – Cornella centre | 19.0 (11.8) | 1955–2010 |
| Warsaw Metro M2 | Warsaw Metro | Poland | Bemowo–Bródno | 18.9km (11.7miles) | 2015–2022 |
| Mexico City Metro Line 3 | Mexico City Metro |  Mexico | La Raza – Universidad | 18.7 (11.62) | 1970–1983 |
| Paris Métro Line 7 | Paris Métro | France | La Courneuve – 8 Mai 1945 – Villejuif – Louis Aragon | 18.3 (11.6) | 1910–1987 |
| Red Line | Baku Metro |  Azerbaijan | – | 18.6 (11.6) | 1967–2002 |
| Line 3 | Barcelona Metro | Spain | Zona Universitària – Trinitat Nova | 18.4 (11.44) | 1925–2008 |
| Line 1 | Shanghai Metro | China | Shanghai South Railway – Shanghai Circus World | 18.1 (11.25) | 1993–2004 |
| Avtozavodskaya Line | Minsk Metro | Belarus | Kamennaya Gorka – Mogilevskaya | 18.1 (11.25) | 1990–2005 |
| U8 | Berlin U-Bahn | Germany | Wittenau – Hermannstraße | 18.1 (11.25) | 1927–1996 |
| Line B | Prague Metro | | Rajská zahrada – Hůrka | 18.0 (11.2) | 1998 |
| Line 2[13] | Athens Metro | Greece | Anthoupoli – Elliniko | 17.9 (11.12) | 2013 |
| Line 5 | Beijing Subway | China | – | 17.8 (11.1) | 2007 |
| Washington, DC Metro Red Line | Washington Metro | United States | Union Station – Medical Center | 17.8 (11.05) | 1984 |
| Line 15 | Beijing Subway | China | – | 17.6 (10.9) | 2014 | - | Metro de Caracas Line 2 Zoológico-El Silencio | Caracas, Venezuela | | 17.5 (10.92) | 1985–1988 --> |
| Tozai Line | Kyoto Municipal Subway | Japan | Uzumasa Tenjingawa-Yamashina-Rokujizo | 17.5 (10.92) | 2008 |
| Line 4 | Barcelona Metro | Spain | Trinitat Nova – La Pau | 17.3 (10.76) | 1908–1999 |
| Kholodnohirsko–Zavodska line | Kharkiv Metro | Ukraine | Kholodna Hora – Industrialna | 17.3 (10.7) | 1975–1978 |
| Milan Metro M3 | Milan Metro |  Italy | Comasina – San Donato | 17.105 (10.62) | 1990–2011 |
| Bucharest Metro Line M2 | Bucharest Metro | Romania | Pipera – Berceni | 17.1 (10.62) | 1986–1987 |
| Tōzai Line | Tokyo Metro | Japan | Nakano–Minami-Sunamachi | 17.0 (10.56) | 1969 |
| M1 | İzmir Metro | Turkey | Kaymakamlık – Basmane
Line is 27 km long, but only 19.8 km of it is underground in two noncontinuous sections. The shorter underground section is 2.9 km long. | 16.9 (10.5) | 2000–2024 |
| Hanzomon Line | Tokyo Metro | Japan | Shibuya-Oshiage | 16.8 (10.4) | 1978–2003 |
| Mexico City Metro Line 1 | Mexico City Metro | Mexico | Observatorio – Pantitlán | 16.7 (10.38) | 1984 |
| Blue Line | Chennai Metro | India | - | 16.6 (10.32) | 2018–2021 |
| Line 9 | Beijing Subway | China | – | 16.5 (10.3) | 2012 |
| Line 17 | Beijing Subway | China | – | 16.5 (10.3) | 2021 |
| L-3 | Madrid Metro | Spain | Villaverde Alto – Moncloa | 16.42 (10.2) | 2007 |
| Line 1 | Chongqing Rail Transit | China | Chaotianmen – Shapingba | 16.4 (10.2) | 2011 |
| Line A | Prague Metro | | Nemocnice Motol – Depo Hostivař
Line is 17.1 km long, but only 16.4 km of it is underground. | 16.4 (10.2) | 2015 |
| Kalininskaya line | Moscow Metro | | Tretyakovskaya – Novokosino | 16.3 (10.1) | 1979–2012 |
| L-4 | Madrid Metro | Spain | Argüelles – Pinar de Chamartín | 16.0 (9.9) | 2007 |
| Sviatoshynsko–Brovarska line | Kyiv Metro | Ukraine | Akademmistechko–Dnipro | 16.0 (9.9) | 1960–2003 |
Seoul Subway Line 7
(shorter section) | Seoul Subway | | Suraksan – Konkuk University | 16.0 (9.9) | 1996 |
| U6 | Berlin U-Bahn | Germany | Alt-Mariendorf – Kurt-Schumacher-Platz | 15.9 (9.86) | 1923–1966 |
| M9 | Istanbul Metro | Turkey | Ataköy – Olimpiyat Viaduct | 15.8 (10.7) | 2013–2024 |
| M3 Line | Copenhagen Metro |  Denmark | Circle route | 15.5km (09.6miles) | 2019 |
| Line 3[14] | Budapest Metro |  Hungary | Határ út–Újpest-központ
Line is 17.39 km long, but only 15.5 km of it is underground. | 15.51NaN1 | 1990 | - | this line is not totally undergroundLine 3 | Athens | Greece | 15.4 (9.6) | 2000-2004 --> |
| Line 1 | Tianjin Metro | China | – | 15.37 (9.55) | 2006 |
| Line 6 | Santiago Metro | Chile | Cerrillos – Los Leones | 15.3 (9.5) | 2017 |
| Paris Métro Line 12 | Paris Métro | France | Front Populaire – Mairie d'Issy | 15.3 (9.5) | 1910–2012 |
| Syretsko–Pecherska line | Kyiv Metro | Ukraine | Syrets – Pivdennyi Bridge | 15.2 (9.4) | 1989–2004 |
| Line 1 (Kolkata Metro) | Kolkata Metro | India | Mahanayak Uttam Kumar -Dum Dum | 15.17 (9.38) | 1984–1995 |
| Line 10 | Chengdu Metro | China | – | 15.0 (9.32) | 2019 |
| Island line | MTR | | Kennedy Town[15] – Heng Fa Chuen | 15.0 (9.32) | | |
| Name | System | Country | Stations | Length | Expected completion |
|---|
| Ligne 15 | Paris Métro | France | Circle route, all underground | 75km (47miles) | 2025–2030 |
| M11 | Istanbul Metro | Turkey | (Phase 2, Kargo Terminali - Halkalı section is 31.5 km in length and is currently under construction, all underground) | 69km (43miles) | Phase 2：2024 |
| Cross Island line | Mass Rapid Transit (Singapore) | Singapore | Linear route with branch section, all underground
(Excludes potential extension from Punggol to Seletar Airport under planning) | 65.5km (40.7miles)
| 2030–2032 |
| Line 13 | Guangzhou Metro | China | Whole lines is underground
(includes Phase II: Chaoyang – Zhucun is 33.6 km and under construction) | 59.2km (36.8miles) | Phase 1：2017
Phase 2：2024 and later |
| L9 / L10 | Barcelona Metro | Spain | | 47.8km (29.7miles)
(incl. branches) | 2009 and 2016 partially;
central section: 2028-2029 |
| Line 13 | Shenzhen Metro | China | Whole line is underground | 45.72km (28.41miles) | Phase 1：2024
Phase 2 (North extension)：2025
South extension：2026 |
| Thomson–East Coast line | Mass Rapid Transit (Singapore) | Singapore | Woodlands North to Sungei Bedok
(Phases 4 and 5, Gardens by the Bay – Sungei Bedok are 13 km in length and are currently under construction, all underground) | 43.4km (27miles) | Phase 4：2024
Phase 5：2025 |
| Line 11 | Guangzhou Metro | China | Circle route, all underground | 43.2km (26.8miles) | 2024 |
| Troitskaya line | Moscow Metro | | Whole line is underground | 40.2km (25miles) | Phase 1：2024 (25km (16miles))
Phase 2：2028–2029 (15.2km (09.4miles)) |
| Athens Metro Line 4 | Athens Metro | | | 38.2km (23.7miles)[16] | 2029 for Phase 1[17] |
| Metro Manila Subway | Manila Metro Rail Transit System |  Philippines | Mindanao Avenue – Ninoy Aquino International Airport (All underground) | 36km (22miles) | 2029 |
| Line 3 | Mumbai Metro | India | Cuffe Parade-SEEPZ | 33.02km (20.52miles) | 2024 for Phase 1 | - Only planned, construction works didn't start yet! Unknown, which parts will be underground. | M3 | İzmir Metro | Turkey | Halkapınar – Menderes | 32.6km (20.3miles) | 2028 --> |
| Line 13 | Chengdu Metro | China | Qiligou – Longhua Temple underground section | 29.07km (18.06miles) | 2024 |
| Line 3 | Chennai Metro | India | Madhavaram Milk Colony – Tharamani | 27.086km (16.83miles) | 2026–2027 |
| D Line Extension | Los Angeles Metro | United States | – | 24.3 km (15.1 mi) | 2025–2026 |
| Line 30 | Chengdu Metro | China | (Phase 1 is 26.28 km) | 26.28km (16.33miles) | 2024 |
| Suburban Rail Loop | Melbourne rail network | Australia | SRL East and North is underground (Cheltenham to Airport) | 26km (16miles) | 2035[18] (Eastern stretch) |
| Metro West | Sydney Metro | Australia | | 24km (15miles) | 2032[19] |
| Metro Western Sydney Airport | Sydney Metro | Australia | | 23km (14miles) | 2026 |
| Blue Line | Stockholm Metro |  Sweden | The extension to Nacka will be around 8 km, all underground, total 22 km including older sections. | 22km (14miles) | 2030 |
| Line 27 | Chengdu Metro | China | Whole line is 24.86 km, but only 17.34 km underground | 17.34km (10.77miles) | 2024 |
| Metro City & Southwest | Sydney Metro | Australia | Chatswood – Sydenham | | 2024[20] | |
