Hermetism refers to a Greco-Egyptian pagan mystical sect, based on the Hermetic Corpus, also known as the Hermetica, a group of 18 tracts composed in Hellenic Alexandria in the first century C.E.

According to literary scholar Harold Bloom, "The Hermetists were Platonists who had absorbed the allegorical techniques of Alexandrian Jewry, and who developed the Jewish speculation concerning the first Adam, the Anthropos or Primal Man, called the Adam Kadmon in Kabbalah, and 'a mortal god' by the Hermetists...."

The Hermetic Corpus became available to the West in 1460, when the documents salvaged from Constantinople surfaced in Florence. Their translation in in1463 (published in 1471) by Marsilio Ficino, set off the great explosion of Renaissance Hermeticism as embodied in John Dee, Giordano Bruno, Tommaso Campanella, Johannes Trithemius, Heinrich Cornelius Agrippa, Robert Fludd, and Theophrastus Bombastus von Hohenheim Paracelsus.

At this time the Hermetic Corpus was seen as being more ancient than both Plato and Pythagoras, though St Augustine thought Hermes lived later than Moses. Whilst Augustine opposed hermeticism, some Renaissance scholars claimed that Hermetic thought was closer to Christianity than those of ancient Greek.

However the claim that hermeticism embodied the oldest wisdom in the world never recovered from the work of Isaac Causabon published in 1614 which showed that the texts were written sometime between 200 and 300 AD by some "semi-christians". This view was based on careful linguistic analysis.

Hermetic magic underwent a 19th century revival in Western Europe, where it was practiced by people such as the Hermetic Order of the Golden Dawn, Aurum Solis and Eliphas Lévi.