Keisei Electric Railway Co., Ltd.

Keisei's first operating line was a human-powered one: on 27 April 1912 it bought the Taishaku push-car tramway between Shibamata and Kanamachi. Its own electric line from Oshiage to a temporary Ichikawa terminal, with a branch from Magarikane (now Keisei-Takasago) to Shibamata, opened on 3 November 1912. Extensions reached Funabashi on 28 December 1916, and Funabashi–Chiba opened on 17 July 1921, giving Keisei a Chiba terminal closer to the city centre than the government railway's. Tsudanuma–Shisui opened on 9 December 1926 and Shisui to the temporary Narita-Hanasakichō station on 24 December, linking Tokyo with Narita; after temple-gate merchants defeated a plan for a station closer to the temple, the present Keisei-Narita station opened on 25 April 1930.

Reaching central Tokyo proved harder: a planned Asakusa extension collapsed after the Keisei scandal of 1928, a bribery affair born of the rivalry with Tobu that saw the company's president and senior executives arrested. Keisei instead absorbed the Tsukuba High Speed Electric Railway on 21 October 1930 and used its Nippori licence to open Aoto–Nippori on 19 December 1931 and Nippori–Ueno Park (now Keisei-Ueno) on 10 December 1933, running beneath Ueno Park in the first underground line of a suburban electric railway in Tokyo. The prewar company diversified widely: power supply from its founding, buses, land sales, the Yatsu Yūen amusement park, and from 1936 a Makuhari meat-processing plant making 'Keisei Ham' and 'Keisei Sausage', with medicines such as a poultice sold by the company itself — the only major private railway to run food and pharmaceutical businesses directly.

In 1942, during the Pacific War, Keisei transferred its power-supply business to Kantō Haiden. Under the Land Transport Business Adjustment Act its affiliate the Sōbu Railway (II) was merged into Tobu, a loss said to have motivated the postwar creation of Shin-Keisei Electric Railway, founded in October 1946 on a former Railway Regiment exercise line won in competition with Seibu. In 1943 the Navy and Railway ministries ordered Keisei to build and run a railway on Japanese-occupied Celebes, and in November 1944 the Navy's Southwest Area civil administration ordered another on Borneo; both were abandoned at the war's end. On 25 June 1945 the company renamed itself Keisei Electric Railway (京成電鉄). Assigned under a 1957 ministry decision to run through to Toei Line 1 (now the Asakusa Line), Keisei regauged its entire network from 1,372 mm to the 1,435 mm standard gauge in stages over the fifty days from 9 October to 1 December 1959 without suspending service, and on 4 December 1960 began through running between Oshiage and Higashi-Nakayama, Japan's first reciprocal through service between a private railway and a publicly operated subway.

Narita then made Keisei an airport railway. Keisei applied in December 1968 for a line to the New Tokyo International Airport, whose construction had been decided in 1966; refused access to the terminal building, it built to a station between the two terminals, finished construction in November 1972, then waited until 1978 as protests delayed the airport's opening. The first-generation AE-series limited express began running between Ueno and Narita on 30 December 1973; on 21 May 1978 the extension to the first Narita Airport Station (now Higashi-Narita) opened and the Skyliner began serving the airport. The oil crisis struck in the middle of this heavy investment and, with aggressive land investment and diversification also backfiring, the company fell into the red: dividends stopped in fiscal 1977, accumulated losses reached 13.3 billion yen in the first half of fiscal 1980 and 28.1 billion yen in the second half of fiscal 1983, and from 1980 to 1990 Keisei endured a 'dark age' unique among the postwar major private railways — 25% staff cuts, the closure of its affiliated department store and asset sales including the Yatsu Yūen site. Restructuring and the success of affiliate Oriental Land — of which Keisei is the largest shareholder — in attracting Tokyo Disneyland turned the company around: a first ordinary profit in twelve years came in the first half of fiscal 1988, the accumulated deficit was cleared in the first half of fiscal 1989, and dividends resumed in the second half.

On 19 March 1991, jointly with JR East, Keisei trains entered the present Narita Airport Station, the old airport station being renamed Higashi-Narita; Keisei also took over the Chiba Express line as the Chihara Line on 1 October 1998. On 17 July 2010 the Narita Sky Access line opened, with the new AE Skyliner running at 160 km/h to link Nippori and Airport Terminal 2 in as little as 36 minutes. On 17 September 2013 the head office moved to Yawata, Ichikawa, in front of Keisei-Yawata Station. After making Shin-Keisei Electric Railway a wholly owned subsidiary in 2022, Keisei absorbed it on 1 April 2025, renaming the Shin-Keisei Line the Matsudo Line; the merger added 26.5 km, bringing the network to eight line sections with 91 stations — the fifth-longest among Japan's major private railways, after Kintetsu, Tobu, Meitetsu and Tokyo Metro.

• 190930 June: the Keisei Electric Tramway was incorporated, two years after the 28 May 1907 grant of the licence for the Oshiage–Narita route applied for in 1903.
• 191227 April: Keisei bought the Taishaku push-car tramway (Shibamata–Kanamachi), its first operating line; 3 November: its own line opened from Oshiage to a temporary Ichikawa terminal, with a branch from Magarikane (now Keisei-Takasago) to Shibamata.
• 192117 July: the Funabashi–Chiba section opened, completing the route to Chiba; Keisei's Chiba terminal stood closer to the city centre than the government railway's station.
• 19269 December: Tsudanuma–Shisui opened, followed on 24 December by Shisui–Narita-Hanasakichō (temporary station), linking Tokyo with Narita; the present Keisei-Narita station opened on 25 April 1930, completing Oshiage–Narita.
• 193310 December: Nippori–Ueno Park (now Keisei-Ueno) opened, achieving the long-sought city-centre terminal via the licence of the absorbed Tsukuba High Speed Electric Railway; the section beneath Ueno Park was the first underground line of a suburban electric railway in Tokyo.
• 194525 June: the company changed its name from Keisei Electric Tramway to Keisei Electric Railway; on 20 February of the same year its lines had been reclassified from tramways under the Tramway Act to railways under the Local Railways Act.
• 19599 October – 1 December: the entire network was regauged from 1,372 mm to the 1,435 mm standard gauge in eleven sections over fifty days, without suspending operations, in preparation for subway through running.
• 19604 December: reciprocal through running began between Oshiage and Higashi-Nakayama with Toei Line 1 (now the Toei Asakusa Line) — Japan's first mutual through service between a private railway and a publicly operated subway.
• 197330 December: limited-express service with the first-generation AE series began between Keisei-Ueno and Keisei-Narita.
• 197821 May: the extension from Narita to the first Narita Airport Station (now Higashi-Narita) opened and the Skyliner began serving the airport; the line had been completed in 1972, but protest movements delayed the airport's opening until 1978.
• 199119 March: jointly with JR East, Keisei trains began serving the present Narita Airport Station inside the airport terminal area via the Komaino junction; the old airport station was renamed Higashi-Narita.
• 201017 July: the Narita Sky Access line opened; the second-generation AE Skyliner began 160 km/h operation, linking Nippori and Airport Terminal 2 in as little as 36 minutes, and station numbering was introduced across the Keisei network the same day.
• 20251 April: Keisei absorbed Shin-Keisei Electric Railway, its wholly owned subsidiary since a share exchange on 1 September 2022, and renamed the Shin-Keisei Line the Matsudo Line; the merger added 26.5 km, bringing the network to 91 stations and the fifth-longest route length among Japan's major private railways.