Sonic X-treme was a platform game developed by Sega Technical Institute from 1994 until its cancellation in 1997. X-treme was intended to be the first fully 3D Sonic the Hedgehog game and the first original Sonic game for the Sega Saturn. Its concepts built on past Sonic games while introducing elements to take Sonic into the 3D era of video games. The storyline followed Sonic on his journey to stop Dr. Robotnik stealing six magic rings from Tiara Boobowski and her father.

X-treme was conceived as a side-scrolling platform game for the Sega Genesis to succeed Sonic & Knuckles (1994). Development shifted to the 32X and then the Saturn and Windows, and the game was redesigned as a 3D platform game for the 1996 holiday season. This plan was disrupted by company politics, an unfavorable visit by Sega of Japan executives, and problems using a game engine developed by Sonic Team. Staff illness made it impossible to finish the game before its deadline, leading to its cancellation.

In its place, Sega released a port of the Genesis game Sonic 3D Blast, but did not release an original 3D Sonic platform game until Sonic Adventure for the Dreamcast in 1998. Sonic X-treme's cancellation is considered an important factor in the Saturn's commercial failure, as it left the system with no original Sonic platform game. Some elements similar to those in X-treme appeared in later games, such as Sonic Lost World (2013).