- Miles "Tails" Prower - Sonic's best friend and former sidekick. The now-grown up fox has become noticeably more mature over the years - not to mention taller - and has long since made a name for himself as the founder of ProwerTech Industries.
- Knuckles the Echidna - A friendly rival of his who occasionally has moments that leaves the hedgehog greatly exasperated. After the total collapse of the Eggman Empire some time after the events of Rage Against the Empire, Sonic hadn’t heard much from the echidna - who was presumed to have returned to his duties as the guardian of the Master Emerald, if not at all.
- Amy Rose - another of Sonic's close friends. People have said that they were much closer before, but a past and undisclosed incident has formed a noticeable rift between the two of them that still lasts to this day...
- Shadow the Hedgehog - while one of Sonic's greatest rivals, he and Shadow are often shown to be very close friends, despite their differences and the fact that the black hedgehog does find himself exasperated at his humor. He also enjoys ribbing him for being shorter than himself, which may simply serve to make him feel better about being shorter than his much younger two-tailed buddy.
- Whirlwind Reyes - The two are shown to be close friends and were fairly close comrades in the endgame of Rage Against the Empire, during which the two first met halfway through. They also very much enjoy one another's company when nothing too important is going on.
- Glacier Von Fang - an old ally he became acquainted with some time before the war against the Eggman Empire, Sonic and Glacier share a healthy friendship with one another. However, the she-wolf’s responsibilities at Neptune City have led to a decrease in their interaction.
- Princess Elise Soleanna III - the would-be sovereign of Soleanna had it not ben for Eggman's sudden attack, he formed an odd friendship of sorts with Elise throughout his adventures in the City of Dawn.
- Zagan the Gravebringer - a tough mercenary with pyrokinetic powers, the two are working together but don’t necessarily see eye-to-eye.
- Prince Friedrich Luminosa - the current monarch of Soleanna, who would have bequeathed his throne to Elise had it not been for a sudden attack by Eggman, Sonic is currently working with Friedrich to put a stop to the doctor's plot. However, he isn't very keen on how secretive about it all he is being...
- Dr. Eggman - Sonic’s late arch-nemesis. Despite a part of him missing the mad doctor’s presence - having had been at it with him for a long time now, he ultimately feels a sense of relief that the evils of Dr. Eggman won’t be around to cause trouble for anyone anymore.
- Infinite - one of Eggman’s prime soldiers during his reign of terror over the planet over a decade ago. Despite earlier comments he himself may have made, the late mercenary did leave enough of an impression on him for the hedgehog to experience small episodes of Post-Traumatic Stress Disorder on occasion.
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