| Name | Place enlisted | No. | Rank | How died | Theatre | Date |
|---|---|---|---|---|---|---|
| Oldfield, Edgar | Halifax, Yorkshire | 33563 | Private | Killed in action | F & F | 10 July 1917 |
| Oliphant, Joseph | Wigton, Cumberland | 241653 | Private | Killed in action | F & F | 12 March 1918 |
| Oliphant, Thomas | Penrith, Cumberland | 28150 | Private | Killed in action | F & F | 2 December 1917 |
| Osborn, John Barwise | Aspatria, Cumberland | 19691 | Private | d. | F & F | 31 May 1916 |
| Osborne, George Henry | Newton Abbot, Devon | 33522 | Private | Died of wounds | F & F | 11 July 1917 |
| Osborne, William | Keswick, Cumberland | 13583 | Private | Killed in action | F & F | 2 October 1918 |
| Ousby, Walter | Penrith, Cumberland | 27995 | Private | d. | F & F | 13 January 1917 |
| Owens, David Evan | Hereford, Herefordshire | 27684 | Private | Killed in action | F & F | 18 November 1916 |
| Owens, John James | Workington, Cumberland | 16435 | Sergeant | Killed in action | F & F | 10 July 1917 |