Sonic the Hedgehog is a video game franchise created and produced by Sega. The franchise centers on a series of speed-based platform games. Sonic, the protagonist, is an anthropomorphic blue hedgehog with supersonic speed, capable of reaching the speed of sound. Typically, Sonic—usually along with some of his friends, such as Tails, Amy, and Knuckles—must stop antagonist Doctor Eggman's plans for world domination.

The first game in the series, released in 1991, was conceived by Sega's Sonic Team division after Sega requested a mascot character. Its success spawned many sequels and helped Sega become one of the leading video game companies during the 16-bit era of the early 1990s.

While the first Sonic games were side-scrolling platform games, later games expanded into other genres, such as Mario & Sonic at the Olympic Games. By 2016, the series had sold over 80 million physical copies, and over 350 million units including software packaged with mobile phone downloads. The franchise has also been spun out into other media, including cartoons, anime, and a comic book series recognized as the longest running based on a video game by Guinness World Records