Waaagh! is a central Ork concept referring to both Ork warbands and the psychic field Orks generate.

The Waaagh! field warps reality to fit Orkish beliefs, allowing their ramshackle technology to function properly. Because the Orks are convinced their designs are sound and functional, the Waaagh! field makes them so. Other races have found that many Orkish devices simply do not work unless wielded by an Orkoid. Similarly, Orks also paint their explosives to make them more destructive and their vehicles red to make them faster; though this may sound nonsensical, because the Orks believe these colors can affect the performance of their weapons, the Waaagh! field makes its true.

Waaagh! is also the name of the massive horde of Orks gathered under a single Warboss – an individual Ork who is the largest, most dominating and physically intimidating. He is able to unite the different warbands of Orks into one massive, almost unstoppable horde.

Both definitions of Waaagh! are named after the standard war cry Orks emit when rallying and charging into battle.