E-123 Omega (or simply Omega) is a fictional character appearing in the Sonic the Hedgehog video game series. Introduced in Sonic Heroes, he is considered a spiritual successor to E-102 Gamma who is part of the same robotics production line in the series. He was created by Doctor Eggman as the last and most powerful E-Series robot, and seeks revenge on him due to resentment of his abilities being wasted.

After Rouge the Bat unwittingly awakened him, he decides to take revenge upon his creator to prove his worth, joining Rouge and Shadow on their quest. Sometime later, he would join his two friends as a part of G.U.N.

"I am E-123, the final and best E-100 unit! Eggman should have sent me to the front lines! He will pay for the insult!"