The U-Foes is a supervillain team appearing in American comic books published by Marvel Comics, usually as enemies of the Hulk. The group consists of four members: Vector, the group's leader, who can repel matter telekinetically; Vapor, who can transform into any form of gaseous matter; X-Ray, who can generate and project radiation and fly; and Ironclad, who has a metallic body and can control his density.

The U-Foes first appeared in The Incredible Hulk (vol. 2) #254 (Dec. 1980) and were created by Bill Mantlo and Sal Buscema. Per The Incredible Hulk (vol. 2) #254's credits, editor Al Milgrom designed the costumes of the U-Foes, while editor-in-chief Jim Shooter helped with the names of the U-Foes.

As noted on the first page of that issue, the group's name was inspired by the 1979 Graham Parker song "Waiting for the UFOs".

Simon Utrecht, a former politician and multi-millionaire, funds an operation to gain superpowers the same way the Fantastic Four had, by flying into space and being exposed to cosmic rays. He chooses three other members to join him: Ann Darnell, her younger brother Jimmy Darnell, and Mike Steel. What the group did not know was that they would be exposed to much higher amounts than the Fantastic Four and that it would most likely kill them. They successfully gain powers, but Bruce Banner brings their ship to safety before they can be killed. Banner transforms into the Hulk and a fight ensues, but the U-Foes lose due to their inexperience with their newly gained powers and inability to fight as a team. In the end, their own ongoing mutations incapacitate them, and the team is scattered as they lose control of their increasing abilities.

Some time later, as their powers stabilize, the U-Foes reunite with the goal of revenge and making a name for themselves in the public eye by killing the Hulk. Though they find the Hulk a more formidable foe, with the intelligence of Bruce Banner then in control of the Hulk, X-Ray discovers a way to keep Banner in his human form by generating 'anti-gamma rays'. The U-Foes imprison Banner at the former Gamma Base and hijack television broadcasts worldwide, intending to gain infamy by killing Banner in front of the world. However, Banner is freed by his allies Betty Ross, Rick Jones, and Bereet, and defeats the U-Foes as the Hulk. Ironically, the U-Foes' attempt to gain fame at the Hulk's expense instead reveals to the world that Banner is in control of the Hulk's power, and leads to a brief period of Banner/Hulk as a popular celebrity and superhero (ending when the Mindless Hulk persona re-asserts itself).

After several defeats at the hands of the Hulk and his allies, each of the U-Foes are banished to a different dimension. They manage to reunite and find their way back to Earth when the mutant Portal's powers manifested. The U-Foes attempt to murder Portal to keep him from opening another portal to banish them, but are defeated by the Avengers. They later attempt to kidnap Portal to exploit his mutant powers, and are defeated once again by Captain America, Darkhawk, and Daredevil.

Throughout the 1980s and 1990s the team generally work alone, but occasionally work as hired hands for other villains. Working for the Leader, they attack the Pantheon, injuring dozens of civilians. Despite the handicap of an orphan girl who had gotten mixed up in the battle, the Hulk and the Pantheon soldiers subdue some of the U-Foes. The villains are tricked into hurting each other. During "Acts of Vengeance", the U-Foes face the West Coast Avengers with the help of Mole Man, but they are defeated.

Around this time, they play an important part in the Vault prison breakout in Marvel Graphic Novel No. 68 - Avengers: Death Trap - The Vault. The various U-Foes work together and with other villains to fight against the prison's security, its forces, Freedom Force and the Avengers. The U-Foes and the other prisoners are neutralized by technological mind-control.