How old is Sonic the Hedgehog

-Video Game
Sonic the Hedgehog was originally 10 years old. He stayed that age until the release of Sonic Adventure, where his age was changed to 15. It has remained that age ever since.

-Comic Series
Sonic the Hedgehog is currently 16 in the comic book series.

The first Sonic game, simply titled "Sonic the Hedgehog" was created in 1991, making the series itself about 20 years old. (2011)