Chaos Hounds (Not to be confused with Flesh Hounds which are Khorne's pet puppies, although they might as well be the same thing) are a type of Chaos Beasts utilized by the forces of Chaos, usually the Lost and the Damned and other Chaos Cults. Brutish and bloodthirsty beasts, the Warhounds of Chaos are tireless hunters built of little more than muscle and fang. These are nightmarish beasts twisted and deformed by the powers of the Warp so that glistening muscle and tissue is visible through their hair and what remains of their skin. However despite their frightening appearance they are agile and strong, capable of catching a man and ripping him to shreds within seconds. They frequently have Ogryn handlers.
Interestingly, Beastmen both from the fantasy and 40k counterparts have a penchant in using these dogs from literal hell. It is unknown why they field them, although a theory includes the familiar kinship that a Beastmen develops with these animals or peerages the beastment are not using chaos hounds, but chaos wolves and the differences is not enough to make them different units. On the field of battle the Beastmen release these feral beasts to intercept the forward elements of the enemy army. Packs of Chaos Warhounds will hunt down and pounce upon enemy skirmishers and scouts, bearing them to the ground and ripping them to pieces in their desperate desire to kill.
Being a form of Chaos Beast, Chaos Hounds are individually unique with each one possessing a mutation or quirk that sets them apart. They form part of the fauna and flora of the Warp and daemon worlds as well. It is unknown whether Chaos Hounds are precursors to Flesh Hounds or whether Khorne drew inspiration from said Chaos Hounds. It is also not known if the Space Wolves ever tried to tame one. But chances are quite likely given their wolf fetish.