Sega Enterprises, Inc. was the parent company of Sega Enterprises, Ltd. and Gremlin Industries. It was established by Gulf+Western and the first game it produced was Bullet Mark.

SEI also traded as "Sega of America", sold electro-mechanical arcade games, sold the Sega-Vision (as part of a short-lived home theater division), and was responsible for the licensing and publishing of home console and computer versions of Sega arcade titles.

The company purchased Gremlin Industries in 1978. This company, eventually becoming "Sega Electronics" was sold to Bally Midway in 1983.

In April 1984 Sega's Japanese arm was purchased by a group of investors including Hayao Nakayama, David Rosen and Isao Okawa, becoming a subsidiary of CSK. The remaining American Sega assets owned by Gulf+Western would then be absorbed; SEI became Simon & Schuster Entertainment Software, Inc. on March 18, 1985 before becoming a shell company, Ages Entertainment Software, Inc. on August 30 of the same year.