Machine God

The Machine God is a theological entity in the Warhammer 40,000 universe. It is worshipped by the Imperial scientists and engineers (known collectively as the Cult of the Machine, or Adeptus Mechanichus) as the bestower of all technology and scientific wisdom. This conflicts with the standart Imperial theology where the only God is the God-Emperor of Mankind and is actually a heresy punishable by death. But since Adeptus Mechanichus is vital to the survival of the Imperium this issue is often avoided by simply dismissing the Machine God as an aspect of the Emperor.

Also there are some hints in the background stories that the Machine God may really exist and may actually be the C'tan Void Dragon, an ancient entity of immense power. It is rumored that the Void Dragon sleeps in a statis-tomb on Mars, which also happens to be the homeplanet of Adeptus Mechanichus.