What is Satanism? The word has functioned as a powerful indictment of one's rivals, an expression of rebellion against authority, and sometimes to describe the deliberate worship of dark, supernatural forces. This Element provides a concise overview of Satanism from its origins in early modern Europe through the present. It covers such topics as legends of the black mass, hell-fire clubs, the Romantic Satanism of Lord Byron and Percy Shelley, and nineteenth-century occultists who expressed reverence for Satan. It describes modern Satanic religions including the Church of Satan, The Temple of Set, The Order of Nine Angles, The Satanic Temple, and others. It also addresses contemporary Satanic Panic from the 1980s through QAnon. This Element should prove useful to anyone seeking to learn more about this complicated and frequently misunderstood tradition.