Odakyu Electric Railway Co., Ltd.

In 1940 the company absorbed Teito Electric Railway, adding today's Keiō Inokashira Line. Facing the loss of its power business to Nippon Hassōden under state control of electricity, the parent Kinugawa Suiryoku Denki absorbed the Odawara Express Railway on 1 March 1941 and relaunched itself as Odakyu Electric Railway Co., Ltd., with a capital of 87.8 million yen. After a Shandong mining venture strained the company, Toshimitsu sold the business to Gotō Keita, and on 1 May 1942 Odakyu was absorbed, with Keihin Electric Railway, into Tōkyō Yokohama Electric Railway, which became Tōkyō Kyūkō Dentetsu — the wartime "Daitōkyū" — in line with the Land Transport Business Coordination Act.

The postwar breakup of Daitōkyū re-created the company: on 1 June 1948 a new Odakyu Electric Railway Co., Ltd. was established with a capital of 100 million yen, buying the former Odakyu lines from Tokyu for 66,351,000 yen as Keiō Teito and Keihin Express were separated at the same time. The Inokashira Line passed to Keiō Teito; instead Odakyu received the Hakone Tozan Railway and Kanagawa Chūō Kōtsū as affiliated companies, and took over part of Tokyu's shareholding in the Enoshima Electric Railway. Non-stop limited express service between Shinjuku and Odawara resumed on 16 October that year, the company was listed on the Tokyo Stock Exchange in May 1949, and through-running over the Hakone Tozan Line to Hakone-Yumoto began on 1 August 1950 via a 6.1 km dual-gauge section from Odawara (Odakyu uses 1,067 mm gauge, Hakone Tozan 1,435 mm).

The limited express fleet became the company's signature. The 1700 series, the first full-fledged Romancecar, entered service on 1 February 1951, and on 6 July 1957 the 3000 series "SE" followed; tested at up to 145 km/h that year, a world speed record for 1,067 mm narrow-gauge lines at the time, it provided data that JNR used for its 151 series limited express EMUs and the 0 Series Shinkansen, and won the first Blue Ribbon Award in 1958. Later generations included the 3100 series "NSE" (1963), 7000 series "LSE" (1980), 10000 series "HiSE" (1987), 20000 series "RSE" (1991), 30000 series "EXE" (1996), 50000 series "VSE" (2005), 60000 series "MSE" (2008) and 70000 series "GSE" (2018). Through services grew in parallel: onto the JNR Gotemba Line from 1 October 1955 via a connecting line at Shin-Matsuda, with the Chiyoda Line of the Teito Rapid Transit Authority (now Tokyo Metro) from 31 March 1978, and with JR Central's Gotemba Line from 16 March 1991.

Rapid economic growth brought explosive population increase and severe crowding along the lines. Odakyu rebuilt Shinjuku Station into the company's first two-level station, with surface and underground platforms, completed on 17 February 1964, and on 1 June 1974 opened the Tama Line from Shin-Yurigaoka to Odakyū-Nagayama to serve Tama New Town, extending it to Odakyū-Tama-Center in 1975 and to Karakida on 27 March 1990. A plan to quadruple-track the inner Odawara Line was first decided in December 1964, but opposition from residents of Setagaya Ward and protracted land acquisition turned it into a half-century undertaking: work got under way on 20 July 1989 with the Kitami–Izumi-Tamagawa section, completed on 23 June 1997; a section including Higashi-Kitazawa–Setagaya-Daita was moved underground on 23 March 2013; and completion of the Yoyogi-Uehara–Umegaoka section on 3 March 2018 finished the quadruple track from Yoyogi-Uehara to Noborito, making all the company's lines within Tokyo double- or quadruple-tracked.

Today Odakyu operates three lines — the 82.5 km Odawara Line, the 27.4 km Enoshima Line and the 10.6 km Tama Line — totalling 120.5 operating kilometres with 70 stations across 27 cities, wards, towns and villages of Tokyo and Kanagawa, an area home to about 5.2 million people. Trains run through onto the Tokyo Metro Chiyoda Line (and, since 26 March 2016, the JR East Jōban Line), the JR Central Gotemba Line and the group's Hakone Tozan Line. PASMO IC ticketing arrived on 18 March 2007, "OH" station numbering from January 2014, and the "EMot" app in 2019 with the company's entry into Mobility as a Service. The Romancecar Museum, the company's first permanent indoor exhibition facility, opened on 19 April 2021, and since February 2023 Odakyu has run a two-headquarters structure in Shinjuku, Tokyo and Ebina, Kanagawa. Within the group's transportation division, the Enoshima Electric Railway — wholly owned since 2019 — and Odakyu Hakone also operate railways.

• 19231 May: the predecessor company Odawara Express Railway Co., Ltd. (Odawara Kyūkō Tetsudō) was founded with a capital of 13.5 million yen, with Toshimitsu Tsurumatsu as president.
• 19271 April: the entire Odawara Line between Shinjuku and Odawara opened, partly single-track, with 38 stations; full double-tracking was completed and express operation began on 15 October.
• 19291 April: the Enoshima Line opened in full, with 13 stations at the time.
• 19411 March: the parent company Kinugawa Suiryoku Denki absorbed the Odawara Express Railway and relaunched itself as Odakyu Electric Railway Co., Ltd., with a capital of 87.8 million yen.
• 19421 May: in line with the Land Transport Business Coordination Act, Odakyu was absorbed together with Keihin Electric Railway into Tōkyō Yokohama Electric Railway, which became Tōkyō Kyūkō Dentetsu (the "Daitōkyū").
• 19481 June: Odakyu Electric Railway Co., Ltd. was re-established with a capital of 100 million yen on its separation from Tōkyō Kyūkō Dentetsu, alongside Keiō Teito Electric Railway and Keihin Express Railway; the Inokashira Line passed to Keiō Teito, while the Hakone Tozan Railway and Kanagawa Chūō Kōtsū joined the Odakyu group.
• 19501 August: through-running over the Hakone Tozan Line to Hakone-Yumoto began, using a dual-gauge arrangement on the section from Odawara.
• 19511 February: the 1700 series entered service as the first full-fledged Romancecar limited express.
• 19576 July: the Romancecar 3000 series "SE" entered service; in tests the same year it reached 145 km/h, a world speed record for 1,067 mm narrow-gauge railways at the time, providing data later used by JNR for the 151 series and the 0 Series Shinkansen.
• 19741 June: the Tama Line opened between Shin-Yurigaoka and Odakyū-Nagayama with five stations; it was later extended to Odakyū-Tama-Center in 1975 and to Karakida on 27 March 1990.
• 197831 March: mutual through services with the Teito Rapid Transit Authority (now Tokyo Metro) Chiyoda Line began, initially between Hon-Atsugi and Ayase.
• 20183 March: quadruple-tracking of the Yoyogi-Uehara–Umegaoka section was completed, finishing the quadruple track between Yoyogi-Uehara and Noborito — a project first decided in December 1964 that took half a century; the 70000 series "GSE" Romancecar entered service on 17 March.
• 202119 April: the Romancecar Museum, the company's first permanent indoor exhibition facility, opened.