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- Dr Miriam O'Connor
- Dr Joy O'Hazy
- Margaret O’Brien-Tomko
- Prof Mike O’Connor AM
- Dr Timothy O’Dowd
- Dr Catherine O’Hare
- Dr Edward O’Mahony
- Jessie O’Mahony
- Dr Robert O’Shea
- Justin M O’Sullivan
- Dr Susannah O’Sullivan
- Prof Andreas Obermair
- Dr Megan Ogilvie
- Dr Jeannie Oliphant
- Dr John Ombiga
- Dr Benjamin A Onyeka
- Dr Cindy Ooi
- Dr Kym Osborn
- Dr Geoff Otton
- Wemi Oyekanmi
- Dr Charlotte Oyston