Onehundredbottlesofbeerphobia Fear of 100 bottles of beer on the wall.
Oneirogmophobia Fear of wet dreams.
Oneirophobia Fear of dreams.
Oneiropolimaphobia Fear of daydreams.
Onomatophobia Fear of hearing a certain word or of names.
Onuxophobia Fear of fingernails and toenails.
Ophidiophobia Fear of snakes.
Ophthalmophobia Fear of being stared at.
Opinatophobia Fear of imagination.
Opiophobia Fear medical doctors experience of prescribing needed pain medications for patients.
Optophobia Fear of opening one's eyes.
Oratoparophobia Fear of speakers.
Orbophobia Fear of the world . (branch of Terraphobia / Planitiphobia)
Ordclaviphobia Fear of computer keyboards.
Ordinophobia Fear of ordinal numbers . (branch of Numerophobia)
Oregonphobia Fear of Oregon . (branch of Americanophobia)
Orlandophobia Fear of Orlando . (branch of Americanophobia)
Ornithophobia Fear of birds.
Orophobia Fear of mountains . (branch of Agoraphobia)
Orthodontophobia Fear of orthodontists.
Orthophobia Fear of property.
Osmophobia Fear of smells or odors.
Osouriphobia Fear of computer mice.
Osphresiophobia Fear of smells or odors.
Ostraconophobia Fear of shellfish.
Otaspidaphobia Fear of earplugs.
Otherkinphobia Fear of otherkin.
Oudenophobia Fear of number 0
Oulinophobia Fear of scars.
Ouranophobia Fear of heaven.
Ouritiriophobia Fear of urinals.
Ovalphobia Fear of ovals.
Ovophobia Fear of eggs . (branch of Cibophobia)