| Name (1649 results) | Rank | Regiment |
|---|---|---|
| O'Leary, Michael | Sergeant | Irish Guards |
| Oliver, Richard Edward Deane | Lieutenant | |
| O'Lone, Robert James | Captain | 2nd Batt. Royal Irish Rifles |
| Olphert, Hugh Montgomery Archdall | Second Lieutenant | 3rd Royal Munster Fusiliers |
| O'Meara, Martin | Private | |
| O'Neill, the Hon. Arthur Edward Bruce | Captain | 2nd Life Guards |
| O'Reilly, Charles Joseph | Captain | Royal Army Medical Corps |
| Ormsby, Gilbert John Anthony | Major | Royal Army Medical Corps |
| Ormsby, Gilbert J. A. | Colonel | Royal Army Medical Corps |
| Orr, Walter Leslie | Second Lieutenant | 4th Batt. Royal Irish Rifles |