X-O Manowar is the title character of a 68-issue comic book series that ran from 1991-1996, and revisited in the limited 6-issue series Unity 2000 in 1999. He was created by Jim Shooter and published under the now defunct Valiant Comics (later Acclaim Comics).

The story follows Aric Dacia, a 5th century Visigoth who was enslaved by the extraterrestrial Spider Aliens. He spent the next fifteen hundred years aboard a Spider Alien spaceship. Do to time-dilation effect of near-light-speed travel, he only aged a couple years. Aric eventually escaped, stealing the Spider Aliens' 'X-O, Manowar Class' body armor in the process. The armour, the (then) supreme variant of the alien's exo-armour research, was able to apart itself to its wearer, making a pyshic or telepathic link thereby enabling it to react at extreme speed to any threat to the wearer. It later became clear that the "manufacture" process for the armour, which appeared not only self-repairing but also capable of spontaneous 'budding' to generate a new version of itself, involved the absorption of a sentient intelligence which became the armour's own sentience.

At first, Aric struggled to adjust to the late-20th-century Earth. He encountered a number of Valiant Universe heroes, befriending some and alienating others. Through a twist of fate, he wound up gaining control of Orb Industries, a dummy corporation founded by Spider Aliens.

When Acclaim Entertainment rebooted all Valiant Comics properties, X-O Manowar was significantly altered. The character was now a modern-day scientist who wielded an X-O armor: an ancient artifact that had wound up in the custody of US government, captured from the Nazis in WW2.

The character was seen in one Acclaim Entertainment-developed video game, Iron Man and X-O Manowar in Heavy Metal, which also featured Marvel Comics' armored superhero Iron Man.