- O'Neill Braden Gregory
- O'Neill Eoin
- Obraczka Katia
- Occhipinti G.
- Ochodo Eleanor
- Odabasi Zekaver
- Offringa Martin
- Ogasawara Eduardo S.
- Ohtsuka Masayuki
- Okwen Mbah Patrick
- Olafson Emily
- Olarte Carlos
- Olaru Sorin
- Oldhafer Karl
- Olin Anna Carin
- Oliu-Barton Miquel
- Oliveira Bárbara
- Oliveira Carla
- Oliveira Fonseca Lucas
- Oliveira Fonseca Lucas
- Oliveira Lucas Emanuel Silva
- Oliveira Raúl
- Oliveira Ricardo C L F
- Oliver Lindsay
- Olivera Christian
- Olivetti Emanuele
- Olivia Keiser
- Olivieri Mario
- Olmo Vaz de Melo Pedro
- Ong David
- Onicas Adrian I
- Onofrey John
- Oostenveld Robert
- Opara Ijeoma
- Orchard Edwina
- Ordonez-Etxeberria I.
- Organero F.
- Orimo Tatsuya