The Fixer is a name used by two villainous fictional characters in the Marvel Comics universe.

The first Fixer was a mobster who was involved in extortion and illegal gambling. He paid boxer "Battling Jack" Murdock to take a fall and lose a fight. Murdock accepted the money, but when he saw his son, Matthew, in the audience, he became determined to continue the fight and eventually won by a knockout. The Fixer's right-hand man, Sweeney, killed Murdock after the fight in retaliation. Matthew Murdock, learning of his father's murder, vowed to bring men like the Fixer to justice, and became the superhero called Daredevil to do so. The Fixer had a fatal heart attack when confronted by Daredevil, and Sweeney was arrested and executed. All of this occurred in the course of Daredevil #1, and was revisited years later in the Daredevil: Yellow miniseries.

The second Fixer is a scientist named Paul Norbert Ebersol, a supervillain and genius-level inventor who has often worked for criminal cartels like HYDRA. In two different incarnations of the Masters of Evil, he was the right-hand man of the team's leader Baron Zemo. In the second of those teams, the team changed their identity to the Thunderbolts, and the Fixer adopted the alias of Techno. Techno was apparently killed when his neck was broken, and he transferred his mind into a robotic body. The robot body was destroyed by the Scourge, who also killed Baron Zemo. The mind of both the Fixer and Zemo were then transferred into the Fixer's original body, although Zemo's mind was soon transferred into another living body. The two of them then rejoined the Thunderbolts.