The Witch Hunters (or Ordo Hereticus) are a part of the Inquisition in the Warhammer 40,000 universe, similar to the Spanish Inquisition. It is their job to root out corruption and blasphemers against the God-Emperor.

These Witch Hunters of the Ordo Hereticus are perhaps the most sinister of all Inquisitors as the threats they must face lurk not in the depths of space or The Warp, but amongst the everyday citizens of the Imperium; the witch, the mutant, the heretic and the fallen cleric.

The Ordo Hereticus, or the state police of the Imperial Cult, use the Orders of the Sisters of Battle (Adeptus Sororitas) as a military wing. After the Age of Apostasy , the Ecclesiarchy were forbidden from maintaining their own military wing, so the Adeptus Sororitas was spun off and formed as a caste of warrior-nuns. On a given field of battle , an Ordo Hereticus Agent can be leading an army of Imperial Guard, Adeptus Sororitas and the countless twisted machines of the ecclisiarchy against the perceived enemy.