The Sega Mega-CD (メガCD) (released as the Sega CD in North America) is an add-on device for the Sega Genesis console, designed and produced by Sega. The device adds a CD-ROM drive to the console, allowing the user to play CD-based games and providing additional hardware functionality. It can also play audio CDs and CD+G discs.
The development of the Mega-CD was confidential; game developers were not made aware of what exactly they were working on until the add-on was finally revealed at the Tokyo Toy Show in Japan. The Mega-CD was designed to compete with the PC Engine CD (TurboGrafx-16 CD) in Japan, which had a separate CD-ROM drive.
The first version of the Mega-CD sits underneath the Mega Drive console and loads CDs via a motorized tray. A second version places a top-loading CD-ROM drive to the right of the console and is intended primarily for use with the redesigned Mega Drive II. Both versions of the Mega-CD are compatible with the initial two versions of the Mega Drive console, but not with the Mega Drive 3 or Genesis 3.