- O'Ferrall, Ernest (1881 - 1925)
- Ogilvie, William Henry (Will) (1869 - 1963)
- Old Boomerang
- see Houlding, John Richard (1822 - 1918) - Oolilee
- see Byrne, Susannah - O'Reilly, Dowell (1865 - 1923)
- O'Reilly, John Boyle (1844 - 1890)
- Osborne, Ernest
- Osmond, Sophie
- Owen, Albert John
- see Owen, Harrison (1890 - 1966) - Owen, Harrison (1890 - 1966)