| Regimental number | 792a |
| Place of birth | Sydney New South Wales |
| True Name | McMAHON, Horace Joseph |
| School | St Patrick's College, Melbourne, Victoria |
| Religion | Roman Catholic |
| Occupation | Labourer |
| Address | Gordon, via Ballarat |
| Marital status | Single |
| Age at embarkation | 21 |
| Height | 5' 5.5" |
| Weight | 136 lbs |
| Next of kin | Miss R. McMahon, Gordon, via Ballarat |
| Previous military service | Nil |
| Enlistment date | |
| Rank on enlistment | Private |
| Unit name | 4th Light Horse Regiment, 3rd Reinforcement |
| AWM Embarkation Roll number | 10/9/2 |
| Embarkation details | Unit embarked from Melbourne, Victoria, on board HMAT A13 Katuna on |
| Regimental number from Nominal Roll | 820 |
| Rank from Nominal Roll | Private |
| Unit from Nominal Roll | 4th Light Horse Regiment |
| Fate | Killed in Action |
| Age at death from cemetery records | 21 |
| Place of burial | Shell Green Cemetery (Plot I, Row B, Grave No 27), Gallipoli, Turkey |
| Panel number, Roll of Honour, Australian War Memorial | 4 |
| Miscellaneous information from cemetery records | Parents: Francis Joseph and Margaret McMAHON, Gordon, Ballarat, Victoria |
| Other details |
War service: Egypt, Gallipoli Admitted to 2nd Light Horse Field Ambulance, 16 October 1915 (tonsillitis); rejoined Regiment, 19 October 1915. Killed in action, 8 November 1915. Medals: 1914-15 Star, British War Medal, Victory Medal |
| Sources | NAA: B2455, CAREY Joseph |