The Cthulhu Mythos is the term used to refer to the stories and legends of the group of nonhuman entities, blasphemous grimoires and paranormal phenomena initially identified (at least as related one another) by H.P. Lovecraft. Other authors such as Robert E. Howard, Clark Ashton Smith and Henry Kuttner, to name but a few, have expanded and deepened the information provided by Lovecraft on these issues.
The term Cthulhu Mythos was coined by August Derleth, who also attempted to systematize the information provided by Lovecraft and others. Some elements of this systematization by Derleth are still controversial among researchers. These include the identification of relatively benevolent Elder Gods as distinct from purely evil Outer Gods and Great Old Ones.
Probably the best-known of these entities is Cthulhu, worshipped by various cultists, human and otherwise. According to legend, Cthulhu is dormant but will one day awaken to reclaim the Earth.
The pantheon as a whole are sometimes referred to as the "Cthulhu Cult Deities". However, despite what the term suggests, Cthulhu is not the central figure nor the most powerful being in this mythological cycle.
Philip José Farmer included elements of Lovecraft's writings in Doc Savage: His Apocalyptic Life, and penned a Mythos story, "The Freshman".