Sakaisuji Line

The line was first envisioned in the Urban Transportation Council's Report No. 3 of 1958 as an underground route from Tenjimbashisuji Rokuchōme to Tenma via Sakaisuji-Hommachi and Dōbutsuen-mae, and — unusually — it was to be operated not by the Osaka prefectural government but by Hankyu Railway. In 1963 the council's Report No. 7 revised the plan, recommending that the southern terminus be placed at Tengachaya rather than Tenma. Later, unrealised proposals would have extended the line to Nakamozu and Sugimotochō, and at one point planners hoped to link the standard-gauge Hankyu and the narrow-gauge Nankai railways by means of dual-gauge track on the Sakaisuji Line; that idea was abandoned because the two companies used different electrification systems.

The Sakaisuji Line opened on 6 December 1969 between Tenjimbashisuji Rokuchōme and Dōbutsuen-mae, a stretch of 7.0 km, and from the first day it ran through-services with Hankyu's Senri Line and Kyoto Main Line; with the new connection, the former ground-level southern terminus of the Hankyu Senri Line at Tenjinbashi was closed. The line opened equipped with automatic train control (ATC) and centralised traffic control (CTC), and was worked at first by five-car trains of the bureau's Class 60 and Hankyu's 3300 series. A line colour was introduced from 8 May 1975.

Through the late 1970s and 1980s the line's services were progressively strengthened. Six-car operation began on 4 March 1979, and the next day a peak-hour "Sakaisuji Express" began running between Dōbutsuen-mae and Kawaramachi (now Kyoto-Kawaramachi) on the Hankyu Kyoto Main Line, the line's first eight-car working and the start of through-running by Hankyu's 5300 series. From 16 December 1989 Hankyu's 7300 and 8300 series began operating onto the line, and the bureau's own 66 series entered service on 1 August 1990. In-car announcements were automated, including on Hankyu trains, from 1 August 1992.

The line was completed on 4 March 1993, when the 1.5 km extension from Dōbutsuen-mae to Tengachaya opened; this served as a subway-based replacement for the Nankai Tennoji Branch Line, which closed the same day. Eight-car operation, begun on the express services and extended to other trains from 21 February 1993, was completed across the line on 7 October 1993, and New Year's all-night running began on 31 December that year. Service patterns were later adjusted several times: the evening Sakaisuji Express became a "Sakaisuji Rapid Express" from 24 March 2001, the Class 60 trains were retired in 2003, and from 17 March 2007 the express and rapid-express services were replaced by a "Sakaisuji Semi-Express".

In the 2010s the line saw further operational changes. On 26 March 2011 train-dispatching was transferred to the central transport control centre, and the automatic approach announcements were updated to the same style as the Chūō Line, with English announcements added at the same time; from 14 May 2011 through-trains to Kawaramachi began running on Saturdays and holidays as well. A timetable revision on 21 December 2013 evened out the morning rush-hour intervals to a uniform three minutes and lengthened the peak period, while pushing back the last trains. Hankyu's 1300 series began operating onto the line from 9 July 2014.

On 1 April 2018 the privatisation of the Osaka Municipal Subway transferred the line to the new Osaka Metro (Osaka City Transportation Co., Ltd.). Platform-edge doors were progressively installed, entering service at Sakaisuji-Hommachi on 29 February 2020 and reaching the last station, Tenjimbashisuji Rokuchōme, on 5 March 2023, by which point every station on the line was equipped. Most recently, through-running by Hankyu's 9300 series began on 14 November 2025.

• 1958The line is first envisioned in Urban Transportation Council Report No. 3 as an underground route from Tenjimbashisuji Rokuchōme to Tenma, to be operated by Hankyu Railway.
• 1963Urban Transportation Council Report No. 7 recommends placing the southern terminus at Tengachaya instead of Tenma.
• 19696 December: the line opens between Tenjimbashisuji Rokuchōme and Dōbutsuen-mae (7.0 km), with through-services to the Hankyu Senri and Kyoto Main lines from day one; ATC and CTC are adopted and five-car trains (Class 60 / Hankyu 3300 series) operate.
• 19758 May: a line colour (vivid brown) is introduced.
• 19794 March: six-car operation begins; the next day a peak-hour 'Sakaisuji Express' starts running through to Kawaramachi on the Hankyu Kyoto Main Line — the line's first eight-car working — and Hankyu 5300 series through-running begins.
• 198916 December: Hankyu 7300 and 8300 series begin operating onto the line, and the 5300 series begins running as local trains.
• 19901 August: the bureau's 66 series enters service.
• 19934 March: the 1.5 km Dōbutsuen-mae–Tengachaya extension opens, completing the line as a subway replacement for the Nankai Tennoji Branch Line, which closes the same day; full eight-car operation is completed on 7 October.
• 200124 March: the evening Sakaisuji Express is reclassified as a 'Sakaisuji Rapid Express'.
• 200717 March: the express and rapid-express services are replaced by a 'Sakaisuji Semi-Express'.
• 201126 March: train-dispatching moves to the central transport control centre and automatic announcements are updated (with English added); from 14 May, Tengachaya–Kawaramachi through-trains also run on Saturdays and holidays.
• 20181 April: with the privatisation of the Osaka Municipal Subway, the line becomes part of Osaka Metro (Osaka City Transportation Co., Ltd.).
• 20235 March: platform-edge doors enter service at Tenjimbashisuji Rokuchōme, completing their installation at every station on the line (begun at Sakaisuji-Hommachi on 29 February 2020).
• 202514 November: through-running by Hankyu's 9300 series begins.