Alpha Grim Sonic, also known as simply Grim Sonic, is an antagonist that appears in the Sonic Prime television series. It is a robot built in the image of Sonic the Hedgehog, used by Nine to be his replacement for Sonic and to combat him and Shadow in the Grim.

Seemingly, Alpha Grim Sonic has very little personality, due to being only made to be an obedient servant to Nine, never talking, and only showing emotion through its eyes. However, it does still display fear.