Sonic X (Japanese: ソニックX, Hepburn: Sonikku Ekkusu) is a Japanese anime television series based on Sega's Sonic the Hedgehog video game series. Produced by TMS Entertainment under partnership with Sega and Sonic Team, and directed by Hajime Kamegaki, Sonic X initially ran for 52 episodes, broadcasting on TV Tokyo from April 2003 to March 2004. A further 26 episodes aired in North America, Europe, and the Middle East from 2005 to 2006. The American localization and broadcasting were handled by 4Kids Entertainment, which edited it and created new music.

The series follows a group of anthropomorphic animals that accidentally teleport from their home planet to Earth after attempting to save one of their friends from their enemy Doctor Eggman. Separated, Sonic the Hedgehog is saved by a human boy named Chris Thorndyke, who helps him find his friends while repeatedly scuffling with Doctor Eggman and his robots over control of the powerful Chaos Emeralds, and becoming celebrities. The final story arc sees Sonic and his friends return with Chris to their world, where they enter outer space with a newfound plant-like creature named Cosmo and fight an army of aliens called the Metarex.

Sonic X received mixed reviews. Generally, reviewers criticized its American localization and the human characters, but praised its story and animation. The series was popular in the United States and France, though less so in its native Japan. The show's merchandise included an edutainment video game for the Leapster, a trading card game, a comic book series featuring an original storyline, and various toys and other items.