IS has attacked Christians, Yazidis, Shiites and other minorities across the region, killing thousands and uprooting ancient communities from ancestral lands.
"They hate difference, whether it is Muslims who think differently, Yazidis or Christians, and because of them the Christians face elimination in the very region in which Christian faith began," the archbishop of Canterbury said in his Christmas Day sermon.
"This apocalypse is defined by themselves and heralded only by the angel of death."
Signup to our newsletter and follow us on Facebook and Twitter!
He likened IS to Herod, who according to historical accounts killed several members of his own family and in the Bible massacred Bethlehem's male infants to prevent the prophesied rise of Jesus.
"To all who have been or are being dehumanised by the tyranny and cruelty of a Herod or an ISIS, a Herod of today, God's judgement... promises justice," Welby said, using another acronym for IS.
The group strictly enforces an austere and bloody form of what it calls Islamic law, tolerating no minority sects or even opposing points of view from their Sunni Muslim co-religionists.
The Middle East is home to ancient Christian and other minority communities, but their numbers have diminished rapidly in recent years amid war and mounting religious intolerance.