"Sonic.exe" is a creepypasta story originally written by JC-the-Hyena, a user on the Creepypasta Wiki, about a cursed CD-ROM version of the first Sonic the Hedgehog game, notable for its malicious depiction of Sonic, giving him black eyeballs with glowing red pupils. The story became popular partly through a genuine appreciation of the story's content and scariness, and from those mocking the extremely poor quality of its writing, which has also been described as amateur and cliched, and later led to it being removed from the Creepypasta Wiki. Sonic.exe received two lesser-known sequels, a rebooted story in 2017, many unofficial games based off of it, as well as other tributes and parodies. JC-the-Hyena would later resign from authoring new Sonic.exe projects after multiple allegations of pedophilic and predatory behavior surfaced in 2021, with the story's fan communities taking control of it since.

The story became so popular and attached to the wider Sonic franchise that the official Sonic the Hedgehog Twitter account has referenced the story on two separate occasions. The first was on January 13, 2017, where they posted a video of Sonic standing in Green Hill Zone as a black recolor of Big the Cat passes him by, changing him and the environment to something more akin to what is depicted in the story. The second was on April 14, 2021, where they posted an image of a pile of Game Gear Sonic titles, with Sonic.EXE being hidden within the pile.