| Surname | Forename | Rank | Unit | Born | Resided |
| O'REILLY | Frank Power | Lieutenant | H.M.S. "Invincible" | Native of Dublin | |
| O'REILLY | Edward | Rifleman | Royal Irish Rifles | Born Stillorgan, Co. Dublin | Resided Stillorgan, Co. Dublin |
| O'REILLY | Edward | Private | Royal Dublin Fusiliers | Born Inchicore, Dublin | |
| O'REILLY | Henry | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'REILLY | James | Lance Corporal | Royal Dublin Fusiliers | Born Dublin | |
| O'REILLY | John | Rifleman | Royal Irish Rifles | Born Dublin | Resided Anderston, Glasgow |
| O'REILLY | Lawrence | Private | Household Cavalry and Cavalry of the Line (including Yeomanry) | Born Dublin | Resided Dublin |
| O'REILLY | Matthew | Private | Royal Fusiliers (City Of London Regiment) | Born Dublin | Resided Dublin |
| O'REILLY | Patrick | Private | Royal Dublin Fusiliers | Born Crumlin, Dublin | Resided Crumlin |
| O'REILLY | Terence | Private | Prince of Wales's Leinster Regiment (Royal Canadians) | Born Dublin | Resided Dublin |
| O'REILLY | Thomas | Private | Princess Victoria's (Royal Irish Fusiliers) | Born Dublin | |
| O'REILLY | Thomas | Lance Corporal | Irish Guards | Born Terenure, Co. Dublin | |
| O'REILLY | Thomas | Private | Royal Dublin Fusiliers | Born Crumlin, Co. Dublin | |
| O'REILLY | Thomas | Private | Royal Army Medical Corps | Born Dublin | |
| O'REILLY | William John | Private | Royal Irish Regiment | Born Dublin | Resided Killeshandra, Co. Cavan |
| O'REILLY | Michael | Sapper | Corps of Royal Engineers | Born Swineford, Co. Mayo | Resided Dublin |
| O'ROURKE | John | Private | Princess Victoria's (Royal Irish Fusiliers) | Born Dublin | |
| O'ROURKE | John | Private | Prince of Wales's Leinster Regiment (Royal Canadians) | Born Dublin | |
| O'ROURKE | John Joseph | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'ROURKE | Peter | Lance Corporal | Irish Guards | Born Dublin | |
| O'ROURKE | Thomas | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'ROURKE | Thomas | Private | Connaught Rangers | Born Howth | Resided Howth, Co. Dublin |
| O'SHAUGHNESSY | James | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'SHEA | Lawrence | Private | Royal Dublin Fusiliers | Born Dublin | Resided Athy |
| O'SHEA | William Theodore | Private | Connaught Rangers | Born Dublin | |
| O'SHEA | Charles | Private | Irish Guards | Born Knockroghery, Co. Roscommon | Resided Dublin |
| O'SULLIVAN | John Anthony | Second Lieutenant | 1st Squadron Royal Flying Corps and General List | | |
| O'SULLIVAN | Daniel J. | Private | Irish Guards | Born Swords, Co. Dublin | |
| O'SULLIVAN | James | Private | Connaught Rangers | Born Dublin | Resided Dublin |
| O'SULLIVAN | Patrick | Private | Irish Guards | Born Dublin | |
| O'SULLIVAN | Francis | Private | Cheshire Regiment | Born Bovis Crannagh, Leinster | Resided Dublin |
| O'TOOLE | Patrick | Fireman | S.S. "Leinster" (Dublin) | Born at Dún Laoghaire, Co. Dublin | |
| O'TOOLE | Alfred | Private | Royal Inniskilling Fusiliers | Born Dublin | |
| O'TOOLE | Christopher | Corporal | Household Cavalry and Cavalry of the Line (including Yeomanry) | Born Maynooth, Dublin | |
| O'TOOLE | Gerald | Private | Labour Corps | Born Dublin, Ireland | |
| O'TOOLE | James | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'TOOLE | James | Gunner | Royal Horse Artillery and Royal Field Artillery | Born Dublin | |
| O'TOOLE | James | Sergeant | Royal Dublin Fusiliers | Born Dublin | |
| O'TOOLE | James | Rifleman | Royal Irish Rifles | Born Dublin | Resided Templelogue, Co. Dublin |
| O'TOOLE | John | Private | Royal Army Medical Corps | Born Dublin | |
| O'TOOLE | John | Lance Corporal | Royal Dublin Fusiliers | Born Swords, Co. Dublin | Resided Swords |
| O'TOOLE | John | Private | Prince of Wales's Leinster Regiment (Royal Canadians) | Born Dublin | |
| O'TOOLE | John | Rifleman | Royal Irish Rifles | Born Dublin | Resided Maryboro', Queen's Co. |
| O'TOOLE | John J. | Sergeant | Irish Guards | Born Dublin | |
| O'TOOLE | Lawrence | Private | Royal Inniskilling Fusiliers | Born Dublin | Resided Dublin |
| O'TOOLE | Michael | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'TOOLE | Michael | Rifleman | Royal Irish Rifles | Born Dublin | |
| OGLESBY | Albert | Private | Princess Victoria's (Royal Irish Fusiliers) | Born Dublin | |
| ORANGE | John | Fireman | S.S. "Lusitania" (Liverpool) | | |
| ORCHARD | Albert George | Pioneer | Hampshire Regiment | Born Dublin | Resided Hastings, Sussex |