Sonic the Hedgehog 3 (ソニック・ザ・ヘッジホッグ3 Sonikku za Hejjihoggu Surī?) is a 1994 platform video game in the Sonic the Hedgehog series for the Sega Genesis. It was developed in the United States by members of Sonic Team working at Sega Technical Institute, and was published by Sega, debuting worldwide in the first half of 1994. The game is a sequel to the Sonic the Hedgehog 2 for the same system and follows on directly from the end of the game, in which Sonic defeated his enemy, Dr. Robotnik; crash-landing on a floating island, Sonic encounters new character Knuckles the Echidna, and must once more retrieve the Chaos Emeralds while also working to stop Dr. Robotnik from relaunching his ship, the Death Egg.

The game is closely tied to its direct sequel Sonic & Knuckles, as the two games were originally developed as a single game until time constraints and cartridge costs forced them to be split into two interlocking parts.