Shadow the Hedgehog is a character appearing in Sega's Sonic the Hedgehog franchise. Shadow was created by Takashi Iizuka and Shiro Maekawa and first appeared in Sonic Adventure 2 (2001). Although this was intended to be his only appearance, Shadow proved so popular among fans that developer Sonic Team decided to include him in Sonic Heroes (2003). Shadow has since featured in numerous entries in the franchise, including the spin-off Shadow the Hedgehog (2005). He also appears in Sonic film and television adaptations, comics, and merchandise.

Within the Sonic franchise's fictional universe, Shadow is an artificial, anthropomorphic black hedgehog created 50 years before titular character, Sonic the Hedgehog was born, by Professor Gerald Robotnik, the grandfather of series antagonist Doctor Eggman. After witnessing the death of his best friend Maria, Shadow vows to keep his promise to her that he would protect the world from danger. As an antihero, Shadow has good intentions but will do whatever it takes to accomplish his goals, putting him at odds with series protagonist Sonic the Hedgehog. Shadow shares many attributes with Sonic and controls similarly in games, but is distinguished by his use of vehicles and firearms.

The idea for Shadow originated during the development of the original Sonic Adventure, with Iizuka and Maekawa ensuring he would be a subtle, "cool" character players could care about. Although Shadow is one of the series' most popular characters and was named one of the greatest video game characters by Guinness World Records in 2011, he has proven divisive among video game journalists. Some have praised his role in Sonic Adventure 2 and his levels' preservation of the Sonic theme, but others have criticized his dark characterization. The Shadow game sold well, but received generally unfavorable reviews.