Sonic the Hedgehog is a video game series released by Sega starring and named after its mascot character, Sonic The Hedgehog. The series began in 1991 with the release of Sonic the Hedgehog on the Sega Mega Drive/Genesis, in addition to an 8-bit version of the game for the Master System and Game Gear formats. Sonic was responsible for turning Sega into a leading video game company during the 16-bit era, and his first game soon replaced Altered Beast as the default pack-in game for the Mega Drive/Genesis in North America and Europe.The series has sold 70 million units worldwide as of 2010.
The Sega division responsible for the first game in the series was called Sonic Team, and the group has since developed many titles in the franchise. Prominent members of its initial staff included programmer Yuji Naka, designer Naoto Ohshima and game planner Hirokazu Yasuhara. Other developers of Sonic games have included American Sega Technical Institute, Japanese Dimps, Canadian BioWare, and British Traveller's Tales. While the first games in the series were platform games, the series has expanded into other genres such as action-adventure, fighting, racing, role-playing, and sports.