Sega Games Co., Ltd.[a] (/ˈsɛɡə/; stylized as SEGA)[b] is a Japanese multinational video game developer and publisher headquartered in Tokyo. Its international branches, Sega of America and Sega Europe, are respectively headquartered in Irvine, California and London. Sega's arcade division, once part of Sega Corporation, has existed as Sega Interactive Co., Ltd., also a Sega Holdings subsidiary, since 2015.

Sega was founded by Martin Bromley and Richard Stewart as Nihon Goraku Bussan[c] on June 3, 1960. The company became known as Sega Enterprises, Ltd. after acquiring Rosen Enterprises, an importer of coin-operated games. Sega developed its first coin-operated game with Periscope in the late 1960s. In 1969, Sega was sold to Gulf and Western Industries. Following a downturn in the arcade business in the early 1980s, Sega began to develop video game consoles, starting with the SG-1000 and Master System, but struggled against competitors such as the Nintendo Entertainment System. In 1984, Sega executives David Rosen and Hayao Nakayama led a management buyout of the company with backing from CSK Corporation.

Sega released its next console, the Sega Genesis (known as the Mega Drive outside North America), in 1988. Although it was a distant third in Japan, the Genesis found major success after the release of Sonic the Hedgehog in 1991 and briefly outsold its main competitor, the Super Nintendo Entertainment System, in the U.S. However, later in the decade, Sega suffered commercial failures such as the 32X, Sega Saturn, and Dreamcast consoles. In 2001, Sega stopped manufacturing consoles to become a third-party developer and publisher, and was acquired by Sammy Corporation in 2004. In the years since the acquisition, Sega has been more profitable, but has been criticized for prioritizing quantity of game releases over quality.

Sega produces multi-million-selling game franchises including Sonic the Hedgehog, Total War, and Yakuza, and is the world's most prolific arcade game producer. It also operates amusement arcades and produces other entertainment products, including Sega Toys. Sega is a subsidiary of Sega Sammy Holdings, a corporate conglomerate with over 60 individual subsidiaries.