Sonic Underground (French: Sonic le Rebelle) is an animated musical television series co-produced by DIC Productions, L.P., Les Studios Tex S.A.R.L. and TF1. It is the third Sonic the Hedgehog animated series, and the last to be produced by DIC. It follows a main plot separate from all other Sonic the Hedgehog media, where Sonic has two siblings, Sonia and Manic, that are collectively part of a royal family who were forced to separate from their mother, Queen Aleena, upon Doctor Robotnik's takeover of Mobius due to a prophecy told by the Oracle of Delphius. Along the way, they encounter other resistance groups against Robotnik and powerful artifacts that could wreak havoc on the world, all the while searching for their long-lost mother, Queen Aleena.

The series first aired in France from January to May 1999 on TF1, and then premiered in the United Kingdom in May 1999 on ITV on the GMTV strand and finally in the United States in the syndicated children's block BKN Kids II from August to October 1999. It also aired on the Sci-Fi Channel on weekday mornings starting October 1999, lasting until October 2000. The show ran only for one season, consisting of forty episodes.