The Sega CD, released as the Mega-CD in most regions outside North America, is a CD-ROM accessory for the Sega Genesis video game console designed and produced by Sega as part of the fourth generation of video game consoles. The add-on was released on December 12, 1991 in Japan, October 15, 1992 in North America, and 1993 in Europe. The Sega CD lets the user play CD-based games and adds extra hardware functionality, such as a faster central processing unit and graphic enhancements. It can also play audio CDs and CD+G discs.

Seeking to create an add-on device for the Genesis, Sega developed the unit to read compact discs as its storage medium. The main benefit of CD technology was greater storage capacity, which allowed for games to be nearly 320 times larger than their Genesis cartridge counterparts. This benefit manifested in the form of full motion video (FMV) games like the controversial Night Trap, which became a focus of the 1993 Congressional hearings on issues of video game violence and ratings. Sega of Japan partnered with JVC to design the add-on and refused to consult with Sega of America until the project was completed. Sega of America assembled parts from various “dummy” units to obtain a working prototype. While the add-on became known for several well-received games such as Sonic the Hedgehog CD and Lunar: Eternal Blue, its game library contained a large number of Genesis ports and FMV titles. The Sega CD was redesigned a number of times, including once by Sega and several times by licensed third-party developers.

By the end of 1994, the add-on had sold approximately 2.7 million units worldwide, compared to 29 million units for the Genesis sold by that time. In 1995, Sega began shifting its focus towards its new console, the Sega Saturn, over the Genesis and Sega CD. The Sega CD was officially discontinued in 1996. Retrospective reception to the add-on is mixed, praising the Sega CD for its individual offerings and additions to the Genesis’ functions, but offering criticism to the game library for its depth issues, high price of the unit, and how the add-on was supported by Sega.