| Name | Date of Birth | Status |
|---|
| O'Brien, Mr Henry | 1 Jan 1793 | Deceased |
| O'Brien, Mr William Joseph | 7 Sep 1882 | Deceased |
| O'Connell, Mr Keith | 24 Nov 1923 | Deceased |
| O'Connell, Sir Maurice Charles | 13 Jan 1812 | Deceased |
| O'Connell, Sir Maurice Charles Philip | 1 Jan 1768 | Deceased |
| O'Connell, The Hon. Hubert David | 12 Apr 1906 | Deceased |
| O'Connor, Mr Joseph Graham | 1 Jan 1839 | Deceased |
| O'Connor, The Hon. Daniel | 13 Sep 1844 | Deceased |
| O'Connor, The Hon. Richard Edward | 4 Aug 1851 | Deceased |
| O'Conor, The Hon. Broughton Barnabas | 1 Nov 1868 | Deceased |
| O'Dea, The Hon. Ernest Charles | 17 Feb 1889 | Deceased |
| O'Doherty, Mr Stephen Mark | 26 Oct 1959 |  |
| O'Grady, Mr Paul Francis | 14 Jul 1960 | |
| O'Halloran, Mr Robert Emmet | 6 Jun 1888 | Deceased |
| O'Hara, Mr Lawrence Joseph | 30 Apr 1889 | Deceased |
| O'Hearn, Mr Walter Finlay | 16 Oct 1890 | Deceased |
| O'Keefe, Mr Frank Lionel | 6 Oct 1912 | Deceased |
| O'Mara, Mr Thomas Chrysostom | 1 Jan 1847 | Deceased |
| O'Neill, Mr Frank | 16 Oct 1893 | Deceased |
| O'Neill, Mr Phillip Joseph | 6 Jun 1941 | |
| O'Regan, Mr John Francis | 8 Feb 1877 | Deceased |
| O'Reilly, Mr Dowell Phillip | 1 Jan 1865 | Deceased |
| O'Reilly, Mr John Francis | 19 Aug 1888 | Deceased |
| O'Reilly, Mr John Joseph | 21 Oct 1888 | Deceased |
| O'Sullivan, Mr Edward William | 17 Mar 1846 | Deceased |
| O'Sullivan, Mr Maurice | 5 Oct 1892 | Deceased |
| Oakeshott, Mr Robert James Murray | 14 Dec 1969 | |
| Oakes, Mr Francis | 1 Jan 1818 | Deceased |
| Oakes, Mr George | 1 Jan 1813 | Deceased |
| Oakes, The Hon. Charles William | 30 Nov 1861 | Deceased |
| Oatley, Mr James | 16 Apr 1817 | Deceased |
| Ogilvie, Mr Edward David Stuart | 25 Jul 1814 | Deceased |
| Olde, Mr Bernard Clarence | 1 Jan 1882 | Deceased |
| Oldfield, The Hon. David Ernest | 25 Jun 1958 | |
| Olliffe, Mr Joseph Benjamin | 10 Sep 1835 | Deceased |
| Onslow, Captain Arthur Alexander Walton | 2 Aug 1833 | Deceased |
| Orkopoulos, Mr Milton | 22 Jul 1957 | |
| Orr, The Hon. Nathanael Montgomery | 8 Oct 1917 | |
| Osborne, Mr Alick | | |
| Osborne, Mr Clive Geoffrey | 18 Mar 1923 | Deceased |
| Osborne, Mr Henry | 8 Feb 1808 | Deceased |
| Osborne, Mr James | 24 Sep 1845 | Deceased |
| Osborne, Mr John Percy | 1 Dec 1878 | Deceased |
| Osborne, Mr Patrick Hill | 20 May 1832 | Deceased |
| Owen, Mr Michael Joseph | 13 Jul 1962 | |
| Owen, Mr Robert | 8 Sep 1799 | Deceased |
| Oxley, Mr Henry Molesworth | 10 Apr 1826 | Deceased |
| Oxley, Mr John Joseph William Molesworth | 1 Jan 1785 | Deceased |
| Oxley, Mr John Norton | 23 Mar 1824 | Deceased |