Shadow the Hedgehog (シャドウ・ザ・ヘッジホッグ, Shadō za Hejjihoggu?) is a recurring character that appears in the anime series Sonic X and its comic series published by Archie Comics. He is a dark doppelgänger hedgehog and the arch-rival of Sonic the Hedgehog. Shadow was created by Gerald Robotnik, and is the end result of Project Shadow. However, the project was closed, and Shadow was captured by G.U.N. and put into stasis on Prison Island after his friend Maria Robotnikwas killed.

Fifty years later, Shadow was awakened from hibernation by Gerald's grandson, Dr. Eggman. Initially, Shadow's goal was to destroy the Earth and avenge Maria's death, but he ultimately decided to save humanity, which almost cost him his life. The black hedgehog later returned to save the universe from destruction. Again, he joins forces with Eggman and Rouge the Bat during the galactic war with the Metarex.

Shadow is extremely arrogant, cold, aggressive, brooding and very loyal to whomever he is serving and determined to whatever cause he is fighting for. He is anti-social and does not speak or smile much. However, he often smirks when being sure of himself, or if he thinks lowly of someone. But deep down, he does have a heart. He cares for those who cared for him such as Maria, Molly, Rouge and Chris Thorndyke and often follows their goals in his own fashion no matter what the cost is. He can be caring to Sonic by showing up and saving Sonic when he needs it the most and genuinely respects him as a rival. Because of his past though, Shadow rarely trusts anyone besides himself. Even when he does, he prefers not to have them get too close to him, lest tragedy should impact him again.

Shadow is easily the most self-sufficient of all the characters. However, his lonesome and arrogant attitude also puts him apart from the other characters. Nevertheless, Shadow can at times be uncaring. For example, when he learned of Cosmo's true mission, he set off to kill her. Shadow, however, did this to try to protect the universe, implying that while he has a good motive, the means used to achieve it are only acceptable to him.

Shadow firmly believes that he is the "Ultimate Life Form" and almost all other life forms are lesser beings and thinks that no one can stand a chance against him. Despite this, he respects a worthy opponent and likes to see someone give him a challenge, apart of why he respects his arch-rival, Sonic.

Shadow only talks when it is absolutely necessary and dislikes being in groups, preferring solitude. Shadow often thinks teamwork is unnecessary because he can handle everything on his own. However, he will help his allies when needed.

Shadow is often depressed about the loss of Maria which is why he keeps to himself, but his relationship with Maria is obvious as he goes to great lengths to protect the planet and keep her dream of peace and prosperity alive. He has also been seen protecting other characters, for example Sonic, Chris, Molly, and Rouge, proving that while his attitude makes him seem like a careless person, he does have some compassion.