Fictional religions are religions that exist only in works of fiction.

B

• Bene Gesserit – Dune series
• Bokononism – Cat's Cradle by Kurt Vonnegut

C

• Carpathianism – Left Behind series
• Chaos Gods  – Warhammer
• Church of All Worlds – Stranger in a Strange Land by Robert A. Heinlein (inspired a non-fictional religious group of the same name)
• Church of Science – the bogus religion established by Salvor Hardin in Isaac Asimov's Foundation
• The Covenant Religion, also known as "The Great Journey" – Halo
• Cthulhu Mythos cults – Cthulhu Mythos
• Cult of Skaro – Doctor Who ^[1]

D

• Dinkoism - based on fictional character Dinkan
• Drowned God - A Song of Ice and Fire

E

• Earthseed – Parable of the Sower and its sequel, Parable of the Talents, see Octavia Butler
• Esoteric Order of Dagon – Cthulhu Mythos

F

• Faith of the Seven – A Song of Ice and Fire

O

• Order of Wen the Eternally Surprised – Discworld
• Old Gods - A Song of Ice and Fire

R

• Robotology – Futurama (Religion in Futurama)

Z

• Zensufi – Dune series
• Zensunni – Dune series