The Royal Army is the military force of the Kingdom of Acorn.
The Royal Army served as the armed forces of the Kingdom of Acorn for an unknown period of time prior to Ivo Robotnik's coup d'état. The army was presumably disbanded after Dr. Ivo "Eggman" Robotnik's deception of King Acorn, which allowed him to gain control of Mobotropolis and most of the kingdom. However, the Knothole Freedom Fighters were later able to overthrow Eggman's dominion of Westside Island, and the army was reformed to protect it. (SSD: #12; FCBD: 2014)
- Royal Palace Guard (Mobotropolis defense forces)
- Knothole Freedom Fighters (mobile special forces team)
- Royal Guard - A branch of the Royal Army charged with protecting the royal family and the city of Mobotropolis.
- Uniforms - the uniform of the Royal palace guard consists of various articles, none of which appear to be mandatory for all participants. Full-ranking members are known to wear white berets.