| Regimental number | 106 |
| Place of birth | Drangan, Tipperary, Ireland |
| Religion | Roman Catholic |
| Occupation | Labourer |
| Address | 296 Wellington Street, Perth, Western Australia |
| Marital status | Single |
| Age at embarkation | 24 |
| Next of kin | Father, Hugh O'Brien, c/o Mrs O'Brien, Mullinhone PO, Mullinhone, Ireland |
| Enlistment date | |
| Date of enlistment from Nominal Roll | |
| Rank on enlistment | Private |
| Unit name | 44th Battalion, A Company |
| AWM Embarkation Roll number | 23/61/1 |
| Embarkation details | Unit embarked from Fremantle, Western Australia, on board HMAT A29 Suevic on |
| Rank from Nominal Roll | Lance Corporal |
| Unit from Nominal Roll | 44th Battalion |
| Fate | Returned to Australia |
| Discharge date | |
| Family/military connections | Brothers: 1639 Bombardier John O'BRIEN, 11th Field Artillery Brigade, returned to Australia, 9 December 1918; 982 Pte Thomas O'BRIEN, 44th Bn, returned to Australia, 17 June 1918. |
| Other details |
War service: Western Front Embarked from Fremantle, 6 June 1916; disembarked Plymouth, England, 21 July 1916. Proceeded overseas to France, 25 November 1916. Wounded in action, 1 June 1917 (gun shot wound, left shoulder); discharged to duty, 12 June 1917. Admitted to hospital, 20 August 1918; transferred to England, 14 September 1918 (enteritis, severe). Discharged from hospital and granted furlough, 7-21 October 1918. Commenced return to Australia on board 'Ceramic', 25 January 1919; disembarked Fremantle, 3 March 1919; discharged, 23 April 1919. Medals: British War Medal, Victory Medal ~ |
| Date of death |