Direction

The completely loop shaped Osaka Loop Line is unable to use the 'up' and 'down' train direction convention commonly applied in Japanese railways – e.g., trains traveling to Tokyo are usually 'up' trains and vice versa. Instead, the words "outer circle" (or outer loop) (外回り, Soto mawari) and the "inner circle" (内回り, Uchi mawari) are used to refer to the direction. The outer is clockwise, the inner counterclockwise.

If rules, such as the registration of the line at the Ministry of Land, Infrastructure, Transport and Tourism apply,^[2] the inner loop is down.

Local

Local trains are operated all day. Some operate over the complete loop, while some serve the eastern half between Osaka and Tennōji via Kyōbashi.

Eight-car EMUs of 323 series are used. 221 series, 223 series and 225 series are used only for morning rush.

Sakurajima Line trains

Trains of the Sakurajima Line (JR Yumesaki Line) are now operated through to the loop line to/from Kyōbashi and Tennoji.

Eight-car 323 series EMUs are used.

Rapids of Kansai Main Line

Through trains to the Kansai Main Line (Yamatoji Line) began operated in 1973. "Yamatoji Rapid" (大和路快速, Yamatoji Kaisoku) and "Regional Rapid" (区間快速, Kukan Kaisoku) trains originate at Tennōji on the loop, passing the loop as "inner" via Osaka, and after stopping at Tennōji after a complete circuit, exit the loop onto the Kansai Main Line and terminate at Kamo, Nara or Ōji. In the loop, Yamatoji Rapids pass some stations while Regional Rapids stop all.

For "Yamatoji Rapid" and "Regional Rapid", usually 8-car and 4+4 car 221 series EMUs are used.

Rapids of Hanwa Line

Trains to the Hanwa Line, "Kansai Airport Rapid" (関空快速, Kankū Kaisoku) for Kansai Airport and Kishūji Rapid (紀州路快速, Kishūji Kaisoku) for Wakayama originate at either Tennoji or Kyobashi, and together with other types of rapid trains, operate on the inner loop via Osaka, pausing at Tennoji and then exiting from the loop. This pattern commenced in 1989, but increased significantly in 1994 on the opening of Kansai Airport.

8-car 223 series and 225 series EMUs in 4+4 formations are used for Kansai Airport and Kishūji rapids. 113 series 4-car units were used for rapids of Shin-Ōsaka - Kii-Tanabe in early morning and late night. They were withdrawn in 2010.

Limited express

Charged Limited Express services such as Haruka for Kansai International Airport, and south bound Kuroshio on the Hanwa Line and Kisei Main Line (Kinokuni Line) heading for the scenic southern Wakayama Prefecture utilize the Osaka Loop Line to bypass the Tōkaidō Main Line and reach the Hanwa Line. On the loop, aside from Tennōji, limited numbers of trains stop only at Nishi-Kujō.

Between the Tōkaidō Main Line and the Osaka Loop Line, trains utilize the Umeda Freight Line [ja] via a new underground route through Ōsaka Station, until it merges the main line at Shin-Ōsaka. This route was introduced in 1989 on the completion of a bypass track from the Hanwa Line to platforms of the Kansai Main Line at Tennōji. Until then no through operations were possible from the Hanwa Line.

281 series and 271 series EMUs are used for Haruka, 283 series EMUs, 287 series EMUs and 289 series EMUs for Kuroshio.

Freight trains

After the abandonment of the Naniwa freight terminal, freight trains on the line operate only between Fukushima and Nishikujō, from the "Umeda Freight Line" to Ajikawaguchi on the Sakurajima Line (JR Yumesaki Line).

Stopping patterns

Stations

• ● : All trains stop.
• ▲ : Stop, outer loop (Tennoji → Nishikujo → Osaka → Kyobashi → Tennoji)
• Number: Track (Platform) numbers to arrive at and depart from.
• | : All trains skip

Local

• 323 series (since 24 December 2016)

The first of a fleet of 21 new 323 series eight-car EMU trains were introduced from 24 December 2016, scheduled to entirely replace the fleet of 23 103 and 201 series trains by 2018.^[3] As of December 2021, few of the remaining 103 series (from Nara Line) and 201 series (Osaka Higashi & Yamatoji Line) continue to be used on the Loop Line.

Yamatoji Rapid, Regional Rapid

• 221 series

Kansai Airport Rapid, Kishūji Rapid, Direct Rapid and Local

• 223 series (0 and 2500 subseries)
• 225 series (5000 and 5100 subseries)

Limited express

• 271 series (Haruka service, from Spring 2020)
• 281 series (Haruka service)
• 283 series (Kuroshio service)
• 287 series (Kuroshio service)
• 289 series (Kuroshio service)

Freight

Locomotives seen hauling freight trains include the M250 series, EF65, EF66, EF81, EF210 and DE10.

Former

Jōtō Line

The Ōsaka to Tennōji via Kyōbashi section (the eastern half of Osaka Loop Line) was opened by the Osaka Railway (大阪鉄道, Osaka Tetsudō) (which also opened the present Minami Osaka Line network) to link it to the Japanese Government Railway (JGR) network in 1895. The line was opened in 2 stages: Tennōji – Tamatsukuri (2 mi. 28 chain, ca. 3.8 km) on 28 May; and Tamatsukuri – Umeda (4 mi. 29 chain, ca. 7.0 km) on 17 October.

Earlier, in 1889, the company opened its main line from Kashiwara – Tennōji – Minatomachi (湊町, present JR Namba) which includes a short section of the Osaka Loop Line, being Tennōji – Imamiya; Imamiya station itself, located between Tennōji and Minatomachi, was opened in 1890.

The Osaka Railway merged with the Kansai Railway (関西鉄道, Kansai Tetsudō, also read as Kansei or Kwansai) in 1900, creating a single entity for the line from Tennōji Station to JGR Ōsaka Station. The Kansai Railway was acquired by the national government in 1907 under the 1906 Railway Nationalization Act. In 1909 the line was named the "Jōtō Line" (城東線, Jōtō sen).

In 1930, distrances were changed to metric, thus the distance changed from 6.6 miles. to 10.7 km. Electrification of the Jōtō Line was commissioned in 1933.

Nishinari Line

The Osaka to Nishi-Kujō section (the northwestern quarter of the line) was built by the Nishinari Railway (西成鉄道, Nishinari Tetsudō) to provide rail access to the Osaka Port. In 1898, the company opened the Osaka – Ajikawaguchi line, which was leased to JGR in 1904. In 1906 the company was nationalized under the act of the same year. In 1909, the line was named the "Nishinari Line" (西成線, Nishinari sen) which included the present-day Sakurajima Line.

The Nishinari Line was electrified in 1941.

Kansai Main Line Freight Line

The Tennōji to Sakaigawa Signal Box (between Taishō and Bentenchō, closed in 2006 when the branch to the port closed) section (south-western portion of the loop) was constructed for freight traffic by the JGR to the port area in 1928, connecting to a freight branch line of the Kansai Main Line, Imamiya – Naniwa (浪速) – Osaka-minato (大阪港, apart from the present Ōsakakō Station on the Osaka Municipal Subway Chūō Line) with a distance of 5.2 mi. (ca. 8.4 km). In 1930 with the change to metric measurement, it became 8.2 km. The former Osaka-Minato and Osaka-Tōkō stations were closed in 1984.

Purpose-built loop line section

To complete the Loop Line, new tracks were constructed between Nishi-Kujō and Sakaigawa Signal Box by the then Japanese National Railways. In 1961, this section opened and the new Osaka Loop Line was named for the entirety of the then Jōtō Line, Osaka – Nishi-Kujō section of the Nishinari Line (the rest, Nishi-Kujō – Sakurajima was named the Sakurajima Line) and the new Nishi-Kujō – Taishō – Tennōji section.

In 1964, operation as a complete Loop Line commenced with the opening of elevated double tracks around Nishi-Kujō. Until then the operation had been undertaken in the shape of a mirrored "6", Sakurajima – Nishi-Kujō – Osaka – Kyōbashi – Tennōji – Nishi-Kujō. The Tennōji – Shin-Imamiya section was quadrupled in 1968, to separate operations from the Kansai Main Line.