Hellspawn are fictional soldiers from Todd McFarlane's comic book series, Spawn. The main character in the series, Spawn, is himself a Hellspawn.
The Hellspawn are controlled by Malebolgia, the ruler of the eighth realm of hell, and are mainly used as an officer corps for hell's army. They were created by Malebolgia and Mammon. Hellspawn are infused with dark energy matter, called Necroplasm, when they are created. This power is infinite while in Hell and finite when outside.
Most Hellspawn were once human, and made a bargain with Malebolgia to return to Earth for either love or vengeance; he would agree to return them to Earth if they promise to become an officer in Satan's Hellspawn army. This deal usually backfires on the Hellspawn, as then Malebolgia would return them to Earth several years (or decades) into the future. The Hellspawn are bonded with a symbiotic armor that protects the Host. Their time on Earth is also limited. Each time a Hellspawn uses his powers it brings him closer to a second death, returning him to hell.
The nature of Hellspawn as generals in hell's army is threefold. Either the Spawn will be a successful murderer and will use his energy to kill innocent and evil alike, thereby providing hell with more souls, or he will try to do good by killing bad people. However, this will only supply hell with the souls of the worst kind of murderers (Kincaid, Wynn, etc.). Alternatively, they will refuse to kill and be destroyed by heaven, in which case hell does not lose anything and will just make another Hellspawn.
Eventually it is revealed that at least the last known Hellspawn are not creation of Malebolgia, but Mammon, trying to enact a breeding program between the most successful bloodlines represented by his Hellspawn. Al Simmons and Wanda, both related to famous Hellspawn of modern times, are the apex of such a process.
There are other Hellspawn such as Daniel Llanso from the Curse of the Spawn spinoff, as well as Ken Kurosawa, Mangler, Cheveyo, and Caleb from the Shadows of Spawn manga, though it is unknown if they are part of the main series' continuity.