| Surname | Forename | Rank | Unit | Born | Resided |
| O'CONNOR | Thomas | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'CONNOR | Thomas | Private | South Wales Borderers | Born Dublin, Ireland | |
| O'CONNOR | Timothy | Private | Royal Dublin Fusiliers | Born Dublin | Resided Dublin |
| O'CONNOR | William | Private | Irish Guards | Born Dublin | |
| O'CONNOR | William | Private | Household Cavalry and Cavalry of the Line (including Yeomanry) | Born Dublin | Resided Dublin |
| O'CONNOR | William | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'CONNOR | James | Private | Royal Dublin Fusiliers | Born Bombay, India | Resided Dublin |
| O'CONNOR | Joseph | Corporal | Corps of Royal Engineers | Born Galway | Resided Dublin |
| O'CONNOR | James | Corporal | Royal Irish Regiment | Born Montreal, Canada | Resided Dublin |
| O'DONNELL | Francis | Private | Royal Dublin Fusiliers | Born Dun Laoghaire, Co. Dublin | Resided Dun Laoghaire |
| O'DONNELL | John Jordan | Private | Royal Welsh Fusiliers | Born Dublin | |
| O'DONNELL | Patrick | Private | Cameronians (Scottish Rifles) | Born Ringsend, Dublin | |
| O'DONNELL | Patrick Joseph | Private | Royal Sussex Regiment | Born Dublin | |
| O'DONNELL | Philip | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'DONNELL | Charles Francis | Lance Corporal | Rifle Brigade (The Prince Consort's Own) | Born Killeybegs, Donegal | Resided Baldoyle, Co. Dublin |
| O'DONOGHUE | John | Private | Royal Dublin Fusiliers | Born Dublin | Resided Chorlton, Manchester |
| O'DOWD | Patrick | Private | Princess Victoria's (Royal Irish Fusiliers) | Born Dublin | |
| O'DOWD | Patrick | Private | Royal Dublin Fusiliers | Born Finglas, Co. Dublin | Resided Dublin |
| O'DRISCOLL | Patrick | Lance Corporal | Royal Dublin Fusiliers | Born Sandyford, Co. Dublin | |
| O'DRISCOLL | Thomas | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'DUFFY | Kevin Emmet | Lieutenant | 7th Battalion, Royal Munster Fusiliers | | |
| O'FARRELL | Archibald Hugh | Second Lieutenant | 1st Battalion, Irish Guards | | |
| O'FARRELL | Maurice | Corporal | Royal Munster Fusiliers | Born Wicklow | Resided Dublin |
| O'FLAHERTY | James | Private | Prince of Wales's Leinster Regiment (Royal Canadians) | Born Dublin | |
| O'FRILL | Francis | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'GORMAN | Francis Prior | Rifleman | London Regiment | Born Dublin | Resided Brixton |
| O'GORMAN | Michael | Acting Sergeant | Royal Dublin Fusiliers | Born Rathmines, Dublin | |
| O'GRADY | Edward | Private | Royal Dublin Fusiliers | Born Dublin | |
| O'GRADY | Hugh | Rifleman | Royal Irish Rifles | Born Dublin | |
| O'GRADY | John | Lance Corporal | Princess Victoria's (Royal Irish Fusiliers) | Born Dublin | |
| O'GRADY | Michael | Private | Royal Dublin Fusiliers | Born Blackrock, Co. Dublin | Resided Blackrock |
| O'GRADY | William | Private | Princess Victoria's (Royal Irish Fusiliers) | Born Dublin | Resided Sheffield |
| O'GRADY | William | Private | Royal Dublin Fusiliers | Born Dublin | Resided Dublin |
| O'HAIRE | Timothy | Private | Royal Dublin Fusiliers | Born Dublin | Resided Dublin |
| O'HALLORAN | Mark Thomas | Gunner | Royal Horse Artillery and Royal Field Artillery | Born Dublin | |
| O'HARA | Patrick Gilbert Warwick | Second Lieutenant | East Surrey Regiment | | |
| O'HARA | Ernest | Private | Connaught Rangers | Born Dublin | Resided Dublin |
| O'HARA | John | Corporal | Connaught Rangers | Born Dublin | Resided Dublin |
| O'HARA | William | Private | Princess Victoria's (Royal Irish Fusiliers) | Born Dublin | |
| O'KANE | Hugh | Private | Royal Inniskilling Fusiliers | Born Dublin | |
| O'KEARNEY-WHITE | Ernest Francis | Second Lieutenant | 9th Battalion, Royal Dublin Fusiliers | | |
| O'KEEFE | Walter | Private | 18th Battalion, Australian Infantry, Australian Imperial Force | Native of Dublin | |
| O'KEEFE | James | Fireman | H.M.S. "Louvain" | | |
| O'KEEFE | Michael | Private | Labour Corps | Born St. James, Dublin | Resided Dublin |
| O'KEEFE | Patrick | Private | Sherwood Foresters (Nottinghamshire and Derbyshire Regiment) | Born Dublin | |
| O'KEEFFE | James | Lance Corporal | Royal Dublin Fusiliers | Born Dublin | |
| O'KEEFFE | Jeremiah | Private | Royal Dublin Fusiliers | Born Dublin | Resided Dublin |
| O'KEEFFE | John | Private | Royal Dublin Fusiliers | Born Castleknock, Co. Dublin | Resided Ballyearton, Co. Wexford |
| O'KEEFFE | Patrick | Private | Princess Victoria's (Royal Irish Fusiliers) | Born Dublin | |
| O'KEEFFE | Patrick | Private | Irish Guards | Born Dublin | |