The Hordes of Chaos (often shortened simply to "Chaos") are a major antagonistic force in Warhammer Fantasy and serve a similiar purpose to the Chaos Space Marines in being the eternal enemies of all humanity stands for, being an army of chaos-obsessed madmen, barbarians, sorcerers and demons of many different forms.

Just like the Chaos Space Marines, the Hordes of Chaos are loyal to the gods of chaos known as Nurgle, Khorne, Slaaneesh and Tzeentch but may also worship lesser Demon Princes or alternatively be loyal to Chaos Undivided.