Earth

Overview
Humans are the dominant species of the earth coexisting with animals and plants just like the real-world modern day Earth. However, sapient animal-like creatures (hailing from an unknown planet), such as Sonic and few others, as well as a number of fictional deities, such as Chaos and Solaris, have made their presence on the planet. Regardless, humans and Sonic-like beings have been shown to live peacefully and are occasionally affiliated with each other. Examples of this include Rouge the Bat and Shadow the Hedgehog who were both part of the human military force Guardian Units of Nations for a brief time.

Although many regions have been seen, the country on Earth that most games take place in appears to be the fictional United Federation, based on the United States of America. In the capital Central City lies a White House-like building with the President as the head of state. Its main military is GUN, which is shown to be a brutal "shoot now, ask questions later" organization that strive for justice but are often clouded in judgment. Some of the planet's larger cities seem to be very advanced and futuristic, as robots and breakthrough technology are commonplace especially to GUN, who create weapons, robots and air fleets primarily to combat the notorious Dr. Eggman.