Unreleased games

Sonic X-treme is perhaps the most infamous of unreleased Sonic games due to the game's troubled development history related to Sega's corporate structure.

Not every video game that is conceived is guaranteed to be finished and sold commercially. Due to various causes such as troubled development, failed location tests or shifts in the video game market, some games could be cancelled at various stages of completion, such as being withheld from release despite development of a game having finalised, a game being cancelled after a prototype had been produced, or a game not even entering development at all. Some of these unreleased games are announced in video game magazines, or kept a secret by the publishers and/or developers.

This category covers all currently known Sonic the Hedgehog games that were in development or considered for development, only to be shelved.