An organization devoted to Dagon, Babylonian sea deity and one of the Great Old Ones in H.P. Lovecraft's pantheon. It was founded by Captain Obed Marsh. Before the fall of Innsmouth, this cult had basically consumed the entire town, completely replacing the freemasons and taking over its hall, along with several churches. Almost the entire non-cult population of the town was eventually driven out or sacrificed.

Father Dagon was worshipped, along with Mother Hydra, by the Deep Ones, an amphibious race of ageless fish-people who had a colony near Devil’s Reef just offshore of Innsmouth, and who had taken great steps towards subverting its population, to the extent of interbreeding with many of its remaining citizens. The Deep Ones were probably responsible for the resurgence of fishing in the town observed after the rise of The Esoteric Order of Dagon.

The head of the Esoteric Order wears “a kind of tall tiara,” which holds special significance to the Deep Ones, as do the dates of April 30th and October 31st. Lovecraft does not describe the vestments used by the Order’s priests, except to say that they were “peculiar” and wore “queer robes.” Many members of the Order have the Innsmouth Look, which indicates Deep One ancestry.

See The Shadow Over Innsmouth.