Sega Corporation is a Japanese multinational video game company and subsidiary of Sega Sammy Holdings headquartered in Shinagawa, Tokyo. It produces several multi-million-selling game franchises for arcades and consoles, including Sonic the Hedgehog, Angry Birds, Phantasy Star, Puyo Puyo, Super Monkey Ball, Total War, Virtua Fighter, Megami Tensei, Sakura Wars, Persona, and Yakuza. From 1983 until 2001, Sega also developed its own consoles.

Having American origins, Sega was founded by Martin Bromley and Richard Stewart as Nihon Goraku Bussan on June 3, 1960. Shortly after, the company acquired the assets of its predecessor, Service Games of Japan. In 1965, it became known as Sega Enterprises, Ltd., after acquiring Rosen Enterprises, an importer of coin-operated games. Sega developed its first coin-operated game, Periscope, in 1966. Sega was sold to Gulf and Western Industries in 1969. 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, with backing from CSK Corporation.

In 1988, Sega released the Mega Drive, or the Genesis in North America. The Mega Drive struggled against competition in Japan, but the Genesis found success overseas after the release of Sonic the Hedgehog in 1991 and briefly outsold its main competitor, the Super Nintendo Entertainment System, in the US. In 2001, after several commercial failures such as the 32X, Saturn, and Dreamcast, Sega stopped manufacturing consoles to become a third-party developer and publisher, and was acquired by Sammy Corporation in 2004. Sega Holdings Co. Ltd. was established in 2015; Sega Corporation was renamed to Sega Games Co., Ltd., and its arcade, entertainment, and toy divisions separated into other companies. In 2020, Sega Games and Sega Interactive merged to become Sega Corporation.

Sega's international branches, Sega of America and Sega Europe are headquartered in Irvine, California, and London. Its development studios include their internal research and development divisions (which utilize the Ryu Ga Gotoku Studio and Sonic Team brands for several core franchise entries), Sega Sapporo Studio which mainly provides support for the Tokyo-based development teams as well as handling partial game development, and Atlus (including their R&D divisions, such as P-Studio and Studio Zero respectively) and five development studios in the UK and Europe: Creative Assembly, Sports Interactive, Sega Hardlight, Two Point Studios, and Rovio Entertainment (including Ruby Games). Sega is one of the world's most prolific arcade game producers and its mascot, Sonic, is internationally recognized. Its name and branding are used for owned or affiliated companies that operate amusement arcades and produce other entertainment products, including Sega Fave; however, these are largely separate ventures. Sega is recognized for its video game consoles, creativity and innovations. In more recent years, it has been criticized for its business decisions and the quality of its creative output.

Being the entertainment contents division of Sega Sammy Holdings, forming one half of the Sega Sammy Group, Sega also owns a toy and amusement machine company, Sega Fave, which comprises their arcade development and manufacturing divisions that were previously under Sega and two animation studios: TMS Entertainment, which animates, produces, and distributes anime such as Lupin the 3rd, Case Closed, and Anpanman & Marza Animation Planet, which specializes in CG animation.