From Jerripedia
| NAME | RANK | NUMBER | UNIT | DATE | |
| OBLIN Arthur John | Able Seaman | 236035(Dev.) | Royal Navy HMS Orion | 06/11/1915 | |
| O’BRIEN Leicester Doras | Corporal | 21561 | Hampshire Regiment 15th Battalion | 07/06/1917 | |
| O’CONNOR Roderic Stratford | Lieutenant | South Staffordshire Regiment 4th Battalion - Attached 2nd Battalion | 28/04/1917 | ||
| OLIVIER Jack | Private | 418108 | London Regiment | ||
| OLIVRY John Alfred | Bombardier | 75959 | Royal Garrison Artillery 23rd Battery 108th Brigade | 28/10/1918 | |
| OLIVRY Sidney John | Lance Corporal | 4233 | Royal Irish Rifles 7th Battalion | 09/09/1916 | |
| OLLIVIER Daniel Bertram | Lance Corporal | 187129 | Canadian Infantry (Manitoba Regiment) 27th Battalion | 16/10/1917 | |
| OLLIVIER William | Private | 45539 | Devonshire Regiment 1st Battalion | 09/05/1917 | |
| OLLIVIER Francois | |||||
| OLLIVIER Pierre Marie | Seaman Gunner - 1st Class | 20678 | French Navy Admiral Charner | 08/02/1916 | |
| ORANGE Walter | Gunner | 199053 | Royal Field Artillery | 24/12/1918 | |
| OSMAND George James Frederick | Sergeant | P/125 | Military Police Corps 8th Division Military Mounted Police | 25/09/1915 | |
| OSMONT Philip | Captain | 19/08/1914 | |||
| OTTLEY Algernon Glendower | Captain | East Yorkshire Regiment 2nd Battalion | 22/05/1915 | ||
| OTTLEY Kendal Coghill Glendower | Lieutenant | West India Regiment 2nd Battalion | 31/10/1916 | ||
| OUNAN Thomas Peter | L8895 | Royal Navy | 06/10/1917 | ||
| OZARD George | Private | 18934 | Devonshire Regiment 9th Battalion | 14/07/1916 | |
| OZARD John Philip | Private | 7907 | Gloucestershire Regiment 1st Battalion | 30/11/1914 | |
| OZARD Thomas Walter Herbert | Lance Corporal | TF/2958 | Middlesex Regiment 1st/8th Battalion | 27/06/1916 | |
| OZOUF Andre Rene | Soldat 2nd Class | 5400 | French Infantry 2nd Battalion African Light Infantry | 19/08/1917 | |
| OZOUF Charles | |||||
| OZOUF Louis Jacques Joseph | Soldat | 2764 | French Infantry 2nd Regiment | 05/10/1914 |
