| Surname | Forename | Rank | Unit | Born | Resided |
| ORCHARD | Patrick | Sergeant | Princess Victoria's (Royal Irish Fusiliers) | Born Dublin | Resided Cavan |
| ORFORD | Thomas | Private | King's (Liverpool Regiment) | Born Dublin | Resided Dublin |
| ORMOND | Patrick | Lance Corporal | Royal Dublin Fusiliers | Born Dublin | |
| ORMONDE | Michael | Sergeant | Princess Victoria's (Royal Irish Fusiliers) | Born Clonmellon, Co. Westmeath | Resided Drumcondra, Co. Dublin |
| ORMSBY | Patrick | Private | Royal Dublin Fusiliers | Born Dublin | |
| ORR | Walter Leslie | Second Lieutenant | 4th Battalion, attached 2nd Battalion, Royal Irish Rifles | | |
| OSBORNE | Charles Robert | Private | Queen's Own (Royal West Kent Regiment) | Born Dublin, Ireland | |
| OTWAY | Thomas William | Private | Household Cavalry and Cavalry of the Line (including Yeomanry) | Born Preston, Sussex | Resided Dublin |
| OULTON | Harry Charles | Second Lieutenant | 4th Battalion, Leinster Regiment | | |
| OVERY | William Coombs | Acting Corporal | Royal Army Service Corps | Birthplace unknown | Resided Dublin |
| OWEN | Richard | Sergeant | Royal Inniskilling Fusiliers | Born St. Michan's, Dublin | |
| OWEN | Thomas Francis | Lance Corporal | Royal Army Service Corps | Born Shrewsbury | Resided Dublin |
| OWENS | Arnold John | Private | Household Cavalry and Cavalry of the Line (including Yeomanry) | Born Dublin | Resided London |
| OWENS | James | Gunner | Royal Horse Artillery and Royal Field Artillery | Born St. Agatha, Dublin | |
| OWENS | Joseph | Lance Corporal | Royal Dublin Fusiliers | Born Dublin | |
| OWENS | Joseph | Private | Royal Inniskilling Fusiliers | Born Inchicore, Dublin | Resided Dublin |
| OWENS | Thomas | Sergeant | Royal Dublin Fusiliers | Born Dublin | Resided Dublin |
| PAGE | John | Lance Corporal | Royal Dublin Fusiliers | Born Dublin | |
| PAGE | Reginald Percy | Company Sergeant Major | Norfolk Regiment | Born St. James, Dublin | |
| PAISLEY | James | Private | Royal Dublin Fusiliers | Born Dublin | |
| PAISLEY | Michael | Private | Royal Dublin Fusiliers | Born Dublin | |
| PAKENHAM | Thomas | Brigadier General | Commanding 2nd (South Midland) Mounted Brigade. General Staff | Born at Dublin | |
| PALMER | Benjamin Norman | Private | Royal Army Service Corps | Born Dublin | Resided Belfast |
| PALMER | Edward | Private | Connaught Rangers | Born Dublin | Resided Dublin |
| PANTON | Arthur William | Second Lieutenant | Corps of Royal Engineers | Born Clontarf, Dublin | |
| PARKER | James | Private | Loyal North Lancashire Regiment | Born Dublin | |
| PARKER | Joseph | Private | Royal Dublin Fusiliers | Born Dublin | Resided Dublin |
| PARKES | Francis | Rifleman | Royal Irish Rifles | Born Dublin | |
| PARKES | Robert | Private | East Lancashire Regiment | Born Rathnew, Dublin | |
| PARKES | Thomas James | Private | Northumberland Fusiliers | Born Dublin | |
| PARKINS | David | Fitter | Royal Garrison Artillery | Born St. Paul's Dublin | |
| PARKINSON | Henry V. | Acting Corporal | Corps of Royal Engineers | Born Dublin | |
| PARKINSON | John | Lance Corporal | Black Watch (Royal Highlanders) | Born Dublin | |
| PARKINSON | Samuel | Lance Corporal | Royal Irish Rifles | Born Dublin | |
| PARSLOW | Laurence | Private (Lance Corporal) | Royal Irish Regiment | Born St. Michael's, Dun Laoghaire, Co. Dublin | |
| PARSONS | Albert | Private | Royal Dublin Fusiliers | Born Dublin | |
| PASLEY | John | Corporal | Connaught Rangers | Born Dublin | Resided Dublin |
| PATCHELL | Francis Vernon | Private | Coldstream Guards | Born Dublin, Ireland | Resided Ealing, Middx. |
| PATCHELL | Matthew | Private | Royal Dublin Fusiliers | Born Dublin | |
| PATERSON | Norman Theodore | Private | 10th Battalion, Canadian Infantry (Alberta Regiment) | | |
| PATON | G. A. L | Captain | 8th Battalion, Northumberland Fusiliers | Born at Dublin | |
| PATTERSON | James | Private | King's (Liverpool Regiment) | Born Liverpool | Resided Dublin |
| PAUL | Alexander Charles | Lieutenant | 11th Battalion, Royal Irish Rifles | | |
| PAUL | Joseph | Rifleman | Royal Irish Rifles | Born Dublin | |
| PAUL | Peter | Private | Royal Dublin Fusiliers | Born Dublin | |
| PAUL | Walter Cecil | Private | Royal Dublin Fusiliers | Born Clontarf, Co. Dublin | |
| PAUL | Cedric Franklyn | Acting Lance Corporal | Royal Sussex Regiment | Killenaule, Ireland | |
| PAXTON | Albert Thomas | Private | Household Cavalry and Cavalry of the Line (including Yeomanry) | Born Dublin | Resided Hampstead |
| PAXTON | George Edward | Private | Household Cavalry and Cavalry of the Line (including Yeomanry) | Birthplace unknown | Resided Dublin |
| PAYNE | William | Private | New Zealand Training Unit | Born in Dublin | |