Sonic the Hedgehog CD is a 1993 platform game developed and published by Sega for the Sega CD. As Sonic the Hedgehog, the player attempts to protect an extraterrestrial body, Little Planet, from Doctor Robotnik. Like other Sonic games, Sonic runs through themed levels while collecting rings and defeating robots. Sonic CD introduces time travel as a game mechanic. By traveling through time, players can access different versions of stages, featuring alternative layouts, music, and graphics.

The Sega CD, known as Mega-CD in most regions outside North America and Brazil, is a CD-ROM accessory for the Sega Genesis produced by Sega as part of the fourth generation of video game consoles. It was released on December 12, 1991, in Japan, October 15, 1992, in North America, and April 2, 1993, in Europe. The Sega CD plays CD games and adds hardware functionality such as a faster CPU and graphic enhancements such as sprite scaling and rotation. It can also play audio CDs and CD+G discs.