Sebastian Acorn is a character mentioned in the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics. He was the tenth king of the Kingdom of Acorn and a member of the House of Acorn.
Succeeding Silvanus Acorn as ruler, Sebastian successfully made peace between the Overland and the Kingdom of Acorn, but is thought to have done so in order to follow his dreams of world exploration. Whatever his intent, he proved a peacemaker across Mobius, helping bring peace to Downunda, which would ever after bow to the authority of the House of Acorn. He also traveled to Mercia, where he helped end a power struggle and establish the ancestors of Rob o' the Hedge as the royal family of that nation.