Sonic the Hedgehog CD or Sonic CD (as it is known in Europe and North America) is a video game that is still well acclaimed by Sonic fans. The game was never touched by Yuji Naka himself; whilst Naka and co. were working on Sonic the Hedgehog 2 at the time, Sonic CD was handled by a separate development team, headed by Sonic creator Naoto Ohshima. This explains why the theme of the game is different.

The game was released for the Sega Mega-CD in Japan on September 23, 1993. It was released in Europe in October 1993. The game was then released for the Sega CD in North America on November 19, 1993.

Sonic the Hedgehog is chasing Metal Sonic, who kidnapped a girl named Amy Rose. It turns out that Amy had used the tarot cards to find Sonic, but was kidnapped in front of his very eyes. Sonic has to get the Time Stones and to travel through time to foil Doctor Robotnik's (Doctor Eggman in the Japanese version) latest plot.

The game's key element was the manner in which the player could travel to 4 different versions of each level in 3 different time periods. This was accomplished by speed posts scattered around the level, saying "Past", and "Future". There were never "Past" signs in the Past and never "Future" signs in the Future. If you destroyed Dr. Robotnik's roboticizer (badnik-making machine) in the past, then you traveled to the future it would be the different "Good Future" with no enemies. You would receive the good ending to the game by completing all the good futures or by collecting the 7 Time Stones in the Special Stages.

The game itself has Sonic feeling generally more sluggish than normal. The spin dash he does is different to that of Sonic 2's; the position he takes in both games is different. A new move was added to complement the spindash: the Super Peelout. The Super Peelout, performed in a manner much the reverse of the spin dash, by pressing up and any trigger button, causes Sonic to rev in position until you release the button, at which point he speeds off. The difference between the spindash and the Super Peelout is the spindash damages enemies who get in its way, due to Sonic's curled attacking pose; the Super Peelout, whilst faster than the spindash, does no damage, instead leaving Sonic vulnerable to attack. Also, while leaving the game idle for more than a few seconds made Sonic tap his foot impatiently, as per usual, leaving the game for 3 minutes caused Sonic (i.e. a digitised voice clip) to say "I'm outta here!", followed by Sonic jumping off the screen and the player receiving a Game Over.

Both the Japanese and American versions of Sonic CD had their own soundtrack. Different people have different tastes about the music. The US version also replaced Amy Rose's name in the manual with that of Princess Sally to garner support for the television show, despite the fact that the Princess Sally character was already established.

Here is a list of rounds:

• Palmtree Panic
• Collision Chaos
• Tidal Tempest
• Quartz Quadrant
• Wacky Workbench
• Stardust Speedway
• Metallic Madness

A version available for the personal computer was released in Japan on August 9, 1996. The North American version came on August 26, 1996, and the European version came on October 3, 1996.

Among the most noteworthy changes of this version was the fact that the entire FMV Anime intro and ending sequence is available for this version. The Mega-CD version only had part of the intro and ending sequence. The Japanese version of the game had its manual translated from the US version.

The American intro and ending music was recorded by a then-popular group named Pastiche.