- Oak, Gabriel
- Obadiah
- Obermann
- Oberon
- objective correlative
- Objectivism
- O'Brallaghan, Sir Callaghan
- Observations on the Present State of the Nation
- Observator
- Observer
- Oceana
- Octavia
- octosyllabics
- The Odd Women
- ode
- ‘Ode on a Grecian Urn’
- ‘Ode to a Nightingale’
- ‘Ode to Autumn’
- ‘Ode to the West Wind’
- O'Dowd, Major
- The Odyssey
- OED
- Of Dramatick Poesy: An Essay
- Og
- ogham
- Ogier the Dane
- Oisin
- The Old Bachelor
- The Old Curiosity Shop
- Old English
