Octophobia - Fear of the figure 8.

Ornithophobia - Fear of birds.

Obesophobia- Fear of gaining weight.(Pocrescophobia)

Ochlophobia- Fear of crowds or mobs.

Ochophobia- Fear of vehicles.

Odontophobia- Fear of teeth or dental surgery.

Odynophobia or Odynephobia- Fear of pain. (Algophobia)

Oenophobia- Fear of wines.

Oikophobia- Fear of home surroundings, house.(Domatophobia, Eicophobia)

Olfactophobia- Fear of smells.

Ombrophobia- Fear of rain or of being rained on.

Ommetaphobia or Ommatophobia- Fear of eyes.

Omphalophobia- Fear of belly buttons.

Oneirophobia- Fear of dreams.

Oneirogmophobia- Fear of wet dreams.

Onomatophobia- Fear of hearing a certain word or of names.

Ophidiophobia- Fear of snakes. (Snakephobia)

Ophthalmophobia- Fear of being stared at.

Opiophobia- Fear medical doctors experience of prescribing needed pain medications for patients.

Optophobia- Fear of opening one's eyes.

Ornithophobia- Fear of birds.

Orthophobia- Fear of property.

Osmophobia or Osphresiophobia- Fear of smells or odors.

Ostraconophobia- Fear of shellfish.

Ouranophobia or Uranophobia- Fear of heaven