Sonic the Hedgehog (ソニック・ザ・ヘッジホッグ, Sonikku za Hejjihoggu?) is the titular main protagonist of the Sonic the Hedgehog series and Sega's mascot. He is an anthropomorphic hedgehog known for his ability to run faster than the speed of sound, hence his name. As his species implies, Sonic can roll up into a concussive ball, primarily to attack enemies. Constantly on the move, Sonic pursues a life of adventures. He has spent most of his life traveling around the world and beyond, usually accompanied by his best friend, Tails. In his journeys, he has defended his world and others from various threats, especially his arch-nemesis, Doctor Eggman. Described as being "like the wind", Sonic is easygoing and honest, but also impatient and short-tempered. He possesses a strong sense of independence and justice, despises oppression, and is loyal to his friends. His many adventures have earned him many titles, allies, and foes, and made him a celebrated hero. However, he remains indifferent to his fame, preferring to live on his own terms.

Miles Prower (マイルス・パウアー, Mairusu Pauā?), better known as Tails (テイルス, Teirusu?), is a character that appears in the Sonic the Hedgehog series. He is an anthropomorphic young fox and Sonic's best friend and sidekick who was born on West Side Island. He can use his tails like helicopter rotors to fly and has a remarkable IQ with excellent mechanical engineering skills. Since they met, Tails has accompanied Sonic in his adventures to thwart their nemesis, Dr. Eggman. Tails is loyal, kind, and curious. In his early years, he was frequently bullied for his twin tails. His life took a positive turn when he met Sonic, forming an unbreakable bond with him. This relationship has made him more confident, growing into a more outgoing, brave, independent individual who strives to become a hero in his own right.

Knuckles the Echidna (ナックルズ・ザ・エキドゥナ, Nakkuruzu za Ekiduna?) is a character that appears in the Sonic the Hedgehog series. He is an anthropomorphic echidna and the current guardian of the Master Emerald as a warrior, a powerful ancient gemstone which is kept on Angel Island. Guarding it is his solemn duty to protect from anyone seeking to abuse it, as well as the last descendant of the Knuckles Clan. Known for his powerful and wild nature, his dominant traits are his super strength and the two spike-like knuckles on each of his gloves, from which his name is derived from, and which he can dig and climb walls with. He can also trap the wind under his dreadlocks to glide through the air. Knuckles is also one of Sonic the Hedgehog's oldest friends and rivals. A loner by nature, Knuckles is independent, headstrong, and serious, yet gullible and short-tempered to a fault. He is entirely devoted to his duty, spending most of his time on Angel Island protecting the Master Emerald, and rarely cares about anything that is of no importance. When his friends and others are in need of his help, however, Knuckles can always be relied on, being willing to leave his home very often.

Amy Rose (エミー・ローズ, Emī Rōzu?), also formerly known as Rosy the Rascal (ロージー・ザ・ラスカル, Rōjī za Rasukaru?), is a character that appears in the Sonic the Hedgehog series. She is an anthropomorphic pink hedgehog with a crush on Sonic the Hedgehog. Since meeting Sonic on Little Planet, Amy has declared herself his girlfriend and has attempted to win his heart by any means in many of their adventures. She wields the Piko Piko Hammer, which she uses with skills second to none and never leaves home without. Amy is a cheerful, though slightly erratic girl, with a positive attitude and nature and boundless energy. However, she has a fiery temper and her infatuation with Sonic makes her short-sighted and a bit obsessive about him, having followed him everywhere since meeting him. Nevertheless, she has a pure heart and will not let anything stop her.

Doctor Ivo Robotnik is the main antagonist of the Sonic the Hedgehog series. A brilliant scientist with an IQ of 300, Dr. Eggman is driven by a desire to conquer the world and establish his own empire, the Eggman Empire. Central to his vision is Eggmanland, an amusement park he seeks to build as the backbone of his regime. His ambitions are fueled by his love of machines and extreme egomania.

Shadow the Hedgehog (シャドウ・ザ・ヘッジホッグ, Shadou za Hejjihoggu?) is a character that appears in the Sonic the Hedgehog series. Characterized by his sharp attitude and strong sense of purpose, Shadow is a recurrent arch-rival of Sonic the Hedgehog, whom he resembles and with whom he shares many abilities. His trademark power is Chaos Control, which allows him to warp time and space using a Chaos Emerald.