The Midōsuji Line (御堂筋線, Midōsuji-sen) is a rapid transit line in Osaka, Japan, operated by the Osaka Municipal Subway. Constructed under Midōsuji, a major north-south street, it is the oldest line in the Osaka subway system and the second oldest in Japan, following the Tokyo Metro Ginza Line. Its official name is Rapid Electric Tramway Line No. 1 (高速電気軌道第1号線), while the Osaka Municipal Transportation Bureau refers to it as Osaka City Rapid Railway Line No.