- O'Neill, Rowan
- Obholzer, Nicci
- Oddy, John A.
- Okwedy, Phil
- Oliver, Reginald Campbell Burn
- Ollerton, Richard L.
- Owen, D. Huw
- Owen, Edwin Augustine
- Owen, Emyr Hywel
- Owen, Gwilym Beynon
- Owen, Hugh
- Owen, Ifor
- Owen, John
- Owen, John
- Owen, John Dyfnallt
- Owen, John Thomas
- Owen, Lyn
- Owen, Morfydd E.
- Owen, Morris Brynllwyn
- Owen, Richard Griffith
- Owen, Robert (Bob)
- Owen, Thomas Richard
- Owen, Trefor M.
- Owen, William Thomas
- Owens, Benjamin George