Sonic the Hedgehog 3 is the 4th Sonic game to be released for the SEGA Mega Drive/Genesis, although chronologically it takes place after the events of Sonic the Hedgehog 2. In this game Knuckles the Echidna is introduced for the first time. Sonic 3 was unique in that this was the first time that players were able to save their progress in a Sonic game.
The game has subsequently been ported to Microsoft's Xbox Live Arcade service and Virtual Console for Nintendo Wii, aswell as included in several compilations:
- Sonic Jam for SEGA Saturn
- Sonic & Knuckles Collection for PC
- Sonic Mega Collection for Nintendo Gamecube
- Sonic Mega Collection Plus for Nintendo Gamecube, Sony Playstation 2 and Microsoft Xbox
- Sega Genesis Collection/Sega Mega Drive Collection for Playstation 3 and Microsoft Xbox 360
- Sonic's Ultimate Genesis Collection/Sega Mega Drive Collection for Sony Playstation Portable
- Sonic Classic Collection for Nintendo DS
After the events of Sonic the Hedgehog 2, Sonic and Tails descend back to the earth after Sonic destroyed the Death Egg. Sonic, as Super Sonic, runs into Knuckles who steals away all the Chaos Emeralds, having been tricked by Dr. Robotnik into believing that Sonic is to be treated as an enemy. Sonic and Tails head out once again to collect the emeralds back from Dr. Robotnik who has teamed up with Knuckles.
 Sonic 3 & Knuckles
The story itself is split into 2 parts, with the second part of Sonic 3 being concluded in. Sonic & Knuckles. The game can be slotted into the Sonic & Knuckles game cartridge and continued directly from the Sonic 3 game save. Slotting Sonic 3 into Sonic & Knuckles also gave players the chance to play as Knuckles through Sonic 3 and Tails to play through Sonic & Knuckles. Additionally, if the player collects all 7 Chaos Emeralds and then all 7 Super Emeralds aswell, Sonic and Knuckles can change into Hyper Sonic and Hyper Knuckles, and Tails into Super Tails.
Sonic 3 plays just like previous traditional Sonic platformers, this time though Tails' abilities have been increased. If a player is controlling Tails they can now fly, or swim underwater, at will, or if playing co-operatively Tails can fly whilst carrying Sonic over short periods of time.
Chaos Emeralds are hidden in Special Zones like usual, although now to access the Special Zone players must locate giant rings hidden within the levels. There is also the addition of a Bonus Stage when the player passes a star post with at least 50 rings, they can enter the bonus stage which is like a giant gumball machine, giving the player the chance to collect rings, lives and various other power-ups.
The game also saw the new edition of 3 varieties of shield:
- Fire shield, which made the player invincible to fire and with a double tap of the jump button gave a boosted horizontal jump
- Water shield, which made the player able to stay under water without drowning and gave the player the ability to bounce to reach higher than with a standard jump.
- Electric shield, this draws rings towards the player, as well as making certain attacks from badniks bounce off the shield and gives an extra boost to jumps.
As well as the co-op play as Sonic and Tails, there is also a split-screen versus mode of 5 unique, short levels which loop on themselves. The aim is to complete the set number of laps of the level before the other player. Players can play as either Sonic, Tails or Knuckles.
 Single Player
- Angel Island Zone
- Hydrocity Zone
- Marble Garden Zone
- Carnival Night Zone
- Ice Cap Zone
- Launch Base Zone
- Special Zone
- Bonus Stage
- Flame Mobile
- Screw Mobile
- Drill Mobile
- Graviton Mobile
- Freezer Mobile
- Ball Machine
- Laser Column
- Big Arms
- Catakiller, Jr.
- Mega Chopper
- Monkey Dude
- Snail Blaster
- Star Pointer
- Turbo Spiker
Music from the game features in the following CD soundtracks: