- Fachen (Irish and Scottish) – Monster with half a body
- Fafnir (Germanic mythology) – Dwarf who was cursed and turned into a dragon. He was later slain by Sigurd in the Saga of Nibelung.
- Fairy (many cultures worldwide, esp. Germanic mythology/folklore) – Nature spirits
- Falak (Arabian) – Giant serpent
- Familiar (English) – Animal servant
- Far darrig (Irish) – Little people that constantly play pranks
- Farfadet (French) – Small (some half-meter tall), wrinkled, and brown-skinned helpful sprites.
- The Fates (Greek) – Three time-controlling sisters
- Faun (Roman) – Human-goat hybrid nature spirit
- Fear gorta (Irish) – Hunger ghost
- Fearsome critters
- Feathered Serpent – Mesoamerican dragon
- Fei Lian (Chinese) – Chinese wind god
- Fenghuang (Chinese) – Chinese Phoenix, female in marriage symbol
- Fenodyree (Manx) – House spirit
- Fenrir (Norse) – Gigantic, ravenous wolf
- Fetch (Irish) – Double or doppelgänger
- Fext (Slavic) – Undead
- Fiery serpents
- Finfolk (Orkney) – Fish-human hybrid that kidnaps humans for servants
- Fir Bolg (Irish) – Ancestral race
- Fire Bird (Many cultures worldwide) – Regenerative solar bird
- Firedrake (Germanic) – Dragon
- Fish-man (Cantabrian) – Amphibious, scaled humanoid
- Flatwoods Monster (American Folklore) (West Virginia) – Alien, humanoid
- Flying Spaghetti Monster
- Fomorian (Irish) – Goat-headed giant
- Forest Bull (Medieval Bestiaries) – Giant horned red cattle
- Four horsemen of the apocalypse
- Frankenstein monster
- Freybug – Norfolk black dog
- Fuath (Celtic) – Malevolent water spirit
- Fucanglong (Chinese) – Underworld dragon
- Funayūrei (Japanese) – Ghosts of people who drowned at sea
- Furu-utsubo (Japanese) – Animated jar
- Futakuchi-onna (Japanese) – Woman with a second mouth on the back of her head
- Fylgja (Scandinavian) – Animal familiar