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. 1(大阪市高速鉄道第1号線), and in MLIT publications it is referred to as Line No. 1 (Midōsuji Line)(1号線（御堂筋線）). On line maps, stations on the Midōsuji Line are indicated with the letter M.
North of Nakatsu it runs above ground in the median of Shin-midōsuji, an elevated freeway.
The section between Senri-chūō and Esaka is owned and operated by Kita-Osaka Kyuko Railway(北大阪急行電鉄,Kita Osaka Dentetsu), but is seamless to the passengers except with respect to fare calculations.
The Midōsuji Line was the first subway line in Osaka and the first government-operated subway line in Japan. Its construction was partly an effort to give work to the many unemployed people in Osaka during the early 1930s. The initial tunnel from Umeda to Shinsaibashi, dug entirely by hand, opened in 1933 after being initially plagued by cave-ins and water leakage caused by the poor composition of the earth below northern Osaka and the equally poor engineering skills of the work crew. The first cars were hauled onto the line by manpower and pack animals from the National Railway tracks near Umeda.
Although the line only operated with single cars at first, its stations were designed from the outset to handle trains of up to eight cars. The line was gradually extended over the next few decades, completing its current length in 1987, making it the second-longest subway line in Osaka after the Tanimachi Line (excluding the Kita-Osaka Kyūkō Railway extension of the Midōsuji Line).
May 20, 1933 - Umeda (temporary station) - Shinsaibashi (opening). Trains started running in single car formation.
October 6, 1935 - Umeda Station (present station) opened.
October 30, 1935 - Shinsaibashi - Namba (opening). Trains started running in 2-car formation.
April 21, 1938 - Namba - Tennōji (opening). Trains started running in 3-car formation.
June 1, 1963 - Trains started running in 8-car formation.
September 1, 1964 - Umeda - Shin-Osaka (opening)
August 29, 1968 - 30 series EMUs began operation.
February 24, 1970 - Shin-Osaka - Esaka together with Kita-Osaka Kyuko Railway (Kitakyu) (opening). This section of track was the first in the Midōsuji Line to utilize Automatic Train Control instead of Automatic Train Stop.
