A guardian angel is a type of angel that is assigned to protect and guide a particular person, group or nation. Belief in tutelary beings can be traced throughout all antiquity. The idea of angels that guard over people played a major role in Ancient Judaism. In Christianity, the hierarchy of angels was extensively developed in the 5th century by Pseudo-Dionysius the Areopagite. The theology of angels and tutelary spirits has undergone many changes since the 5th century. The belief is that guardian angels serve to protect whichever person God assigns them to.

The idea of a guardian angel is central to the 15th-century book The Book of the Sacred Magic of Abramelin the Mage by Abraham of Worms, a German Cabalist. In 1897, this book was translated into English by Samuel Liddell MacGregor Mathers (1854–1918), a co-founder of the Hermetic Order of the Golden Dawn, who styled the guardian angel as the Holy Guardian Angel.

Aleister Crowley (1875–1947), the founder of the esoteric religion Thelema, considered the Holy Guardian Angel to be representative of one's truest divine nature and the equivalent of the "Genius" of the Hermetic Order of the Golden Dawn, the Augoeides of Iamblichus, the Atman of Hinduism, and the Daimon of the ancient Greeks. Following the teachings of the Golden Dawn, Crowley refined their rituals which were intended to facilitate the ability to establish contact with one's guardian angel.