Sega's main offices, as well as the main offices of its domestic division, Sega Corporation (Japan), are located in Ōta, Tokyo, Japan. Sega's European division, Sega Europe Ltd., is headquartered in the Chiswick area of London. Sega's North American division, Sega of America Inc., is headquartered in San Francisco, California; having moved there from Redwood City, California in 1999. Sega Australia's headquarters are located in Sydney, New South Wales. Sega started operations in Australia in the mid 80's as a joint venture with Ozisoft which became Sega Ozisoft until the late 90's when Sega took its shares from Ozisoft after Sega Ozisoft was bought out by Infogrames. Sega Australia is tied with Sega Europe because of the PAL situation, and releases Sega Master System and Sega Mega Drive VC games with Nintendo Australia. Ozisoft was then bought out by Atari. Until 2000, Sega's official corporate name was Sega Enterprises Ltd..

Origins and entry into the video game market (1945–1989)

Sega was founded in 1940 as Standard Games (later Service Games) in Honolulu, Hawaii, by Martin Bromely, Irving Bromberg, and James Humpert to provide coin-operated amusements for American servicemen on military bases. Bromely suggested that the company move to Tokyo, Japan in 1951 and in May 1952 "SErvice GAmes of Japan" was registered.

In 1954, another American businessman, David Rosen, fell in love with Tokyo and established his own company, Rosen Enterprises, Inc., in Japan to export art. When the company imported coin-operated instant photo booths, it stumbled on a surprise hit: The booths were very popular in Japan. Business was booming, and Rosen Enterprises expanded by importing coin-operated electro-mechanical games.

Rosen Enterprises and Service Games merged in 1965 to make Sega Enterprises. Within a year, the new company released a submarine-simulator game called Periscope that became a smash-hit worldwide.

In 1969, Gulf+Western purchased Sega, and Rosen was allowed to remain CEO of the Sega division. Under Rosen's leadership, Sega continued to grow and prosper.

In the video game arcades, Sega was known for games such as Zaxxon and Out Run''.

Sega's revenues would hit $214 million by 1982 and in 1983, Sega would release its first video game console, the SG-1000, the first 3D arcade video game, SubRoc-3D, which used a special periscope viewer to deliver individual images to each eye, and the first action-based laserdisc arcade game, Astron Belt.

In the same year, Sega was hit hard by the American video game crash. Hemorrhaging money, Gulf+Western sold the U.S. assets of Sega to famous pinball manufacturer Bally Manufacturing Corporation. The Japanese assets of Sega were purchased for $38 million by a group of investors led by Rosen and Hayao Nakayama, a Japanese businessman who owned a distribution company that had been acquired by Rosen in 1979. Nakayama became the new CEO of Sega, and Rosen became head of its subsidiary in the United States.