The Great God Pan is a horror and fantasy novella by Welsh writer Arthur Machen. Machen was inspired to write The Great God Pan by his experiences at the ruins of a pagan temple in Wales.
On publication, it was widely denounced by the press as degenerate and horrific because of its implied sexual content, and the novella hurt Machen's reputation as an author. Beginning in the 1920s, Machen's work was critically re-evaluated and The Great God Pan has since garnered a reputation as a classic of horror. Literary critics have noted the influence of other nineteenth-century authors on The Great God Pan and offered differing opinions on whether or not it can be considered an example of Gothic fiction or science fiction. The novella has influenced the work of horror writers such as Bram Stoker, H. P. Lovecraft, and Stephen King, and has been adapted for the stage twice.