Sonic the Hedgehog Megamix (commonly shortened to Sonic Megamix) is a work-in-progress multiperson disassembly modification of the original Sonic the Hedgehog videogame for the Sega Mega Drive / Genesis, headed up by Team Megamix and more recently moved to the Sega Mega CD. Due to this move, a common misconception is that it is a modification of Sonic CD, which is untrue.

The game features the ability to play as one of five different characters - Sonic the Hedgehog, Mighty the Armadillo, Shadow the Hedgehog, Miles "Tails" Prower, and Knuckles the Echidna - and is an extensive reworking of the original game featuring new art, music, abilities, layouts, and more.