| Number | Unit | Name | Rank | Enlistment Date | RTA | Age at Enlistment | Occupation | Marital Status | Locality | Death Date | Memorial |
| 1158 | 3 Bn | O'BRIEN, Branden Charles Joseph | Private | 28 Aug 1914 | 25 | farmer | S | Kembla Heights | 07-12/08/1915 | Scar PC | |
| O'BRIEN, C | Wollongong | Wollongong | |||||||||
| 1452 | 13 Bn | O'BRIEN, Frederick John | Private | 29-Oct-14 | 26 | clerk | S | Gerringong | 11/08/16 | ||
| 6787 | 13 Bn | O'BRIEN, George Thomas | Private | 5-Aug-16 | 19 | quarryman | S | Wollongong | |||
| O'BRIEN, James | Wollongong | Wollongong | |||||||||
| 4751 | 20 Bn | O'BRIEN, James Henry | Private | 7-Dec-15 | 40 | labourer | S | Scarborough | |||
| 330 | 5 MGB | O'BRIEN, James Maurice | Private | traveller | Wollongong | 20/09/17 | Thirroul | ||||
| O'BRIEN, John B | Wollongong | Wollongong | |||||||||
| 5012 | 1 Fld Coy Engineers | O'BRIEN, William Charles Joseph | sapper | 21-Oct-15 | 23 | electrician | S | Unanderra | |||
| 6852 | 13 Bn | O'CONNOR, Daniel Joseph | Private | 25-Sep-16 | 19 | labourer | S | Helensburgh | 11/04/17 | Helensburgh | |
| 359 | 3 Bn | O'CONNOR, James Donald | Private/L/Corporal | 17 Aug 1914 | 24 | blacksmith | S | Helensburgh | 9/04/17 | Helensburgh | |
| O'HALLORAN, C | Thirroul | Thirroul | |||||||||
| 4866 | 55 Bn | O'NEIL, John Joseph | Private | carpenter | Wollongong | 30/11/18 | Wollongong | ||||
| O'NEILL, A | Wollongong | Wollongong | |||||||||
| O'NEILL, H | Thirroul | Thirroul | |||||||||
| 3595 | 17 Bn | O'NEILL, Henry Edward | Private | 29 Aug 1915 | 23 | driver | S | Mount Keira | Wollongong | ||
| 4587 | 30 Bn | O'NEILL, Hughie | Private | 4-Nov-16 | 26 | labourer | S | Thirroul | |||
| 6367 | 13 Bn | O'NEILL, William | Private | 22-Mar-16 | 23 | labourer | S | Jamberoo | |||
| OLDFIELD, E | Shellharbour, Albion Park | Shellharbour C/E, Albion Park CH | |||||||||
| 3700 | 37 Bn | OLIVER, Archibald Cecil | Private | 16-Oct-16 | farmer | Shellharbour | 14/07/17 | Shellharbour C/E, Shellharbour ROH | |||
| OLIVER, O C | Albion Park | Albion Park CH | |||||||||
| OLSEN, A | DL | ||||||||||
| 9199 | Dermatological Hopital | OLSEN, Christian | Private | 25-Jul-15 | 26 | wardman | S | Wollongong | |||
| 8092 | AMC | OLVER, Charles Sedgwick | Private/Corporal | 24-Jun-15 | 12/06/19 | 30 | clergyman | M | Wollongong | Wollongong | |
| 1967 | 53 Bn | ONIONS, Bert | Private | 23-Feb-16 | 22/08/19 | 21 | miner | S | Bellambi | Corrimal Methodist | |
| 6298 | 13 Bn | ONIONS, Reuben James | Private | 6-Apr-16 | 28/06/19 | 25 | miner | S | Russell Vale | Corrimal Methodist | |
| 1507 | Aust Prov Corps | OPREY, Hugh Edward | Private | 7-Sep-15 | 24/07/19 | Thirroul | Thirroul | ||||
| 5191 | 1 Bn | ORGAN, Elias (known as John) | Private | 8/12/15 | RTA 22/09/1919 | 21 | miner | S | Mt Keira | Wollongong | |
| ORGAN, W | Wollongong | Wollongong | |||||||||
| 1917 | 16 Rail Coy | ORVAD, James | Sapper | 31-Oct-14 | 13/05/18 | Kiama | Bulli, WB | ||||
| 3008 | 31 Bn | ORVAD, John Peter | Private | 27-Jan-16 | 18 | labourer | S | Woonona | |||
| OSBORNE, A | Wollongong | ||||||||||
| OSBORNE, E | Unanderra PS | Unanderra PS | |||||||||
| 3287 | 30 Bn | OSBORNE, Ernest William | Private | 23-Nov-15 | 23 | miner | S | Wollongong | Thirroul, Wollongong, Wollongong Meth | ||
| 2717 | 30 Bn | OSBORNE, Norman Carlton | Acting Corporal | 15-Jan-16 | 27 | school teacher | S | Wollongong | Wollongong, Wollongong Meth | ||
| 2696 | 45 Bn | OSBORNE, Thomas Ernest | Private | 12-Jun-16 | 33 | smelter | M | Wollongong | 10/12/16 | Wollongong | |
| 7164 | 18 Bn | OSBORNE, Thomas Erskine | Private | 2-Jun-17 | 37 | farm labourer | S | Unanderra | |||
| OSWALD, E C | Wollongong | Wollongong | |||||||||
| 1378 | Mining Corps | OWEN, Frank | Sapper | 23-Mar-15 | 22 | miner | S | Corrimal | |||
| OWEN, H | Helensburgh | Died | Helensburgh Meth | ||||||||
| OWEN, J | WB | ||||||||||
| 6788 | 13 Bn | OWEN, John | Private | 18-Sep-16 | 38 | labourer | M | Kiama | |||
| 58 Bn | OWEN, Percy Irvine Haylock | 2 Lt | 13/10/15 | 25 | planter | S | Bellambi | 22/09/17 | Wollongong | ||
| 3 Bn | OWEN, Robert Haylock | Lt- Colonel | 20 Aug 1914 | 8/10/15 | 52 | M | Wollongong | Wollongong | |||
| 958 | 18 Bn | OWEN, Stanley Thomas | Private | 1-Mar-15 | 19 | miner | S | Kembla Heights | |||
| OWEN, W G | Woonona-Bulli | WB | |||||||||
| OWENS, Frank | Corrimal | ||||||||||
| 294 | 18 Bn | OWENS, Jack | Private | 2-Feb-15 | 29 | miner | S | Helensburgh | |||
| 559 | 3 Bn | OWENS, Jack | Private | miner | S | Keiraville | |||||
| 1282 | Mining Corps | OWENS, John | Sapper | 8-Jan-16 | 29 | miner | M | Woonona | |||
| OWENS, Leslie | Mount Kembla | ||||||||||
| 4212 | 18 Bn | OWENS, Patrick Joseph | Private | 1-Nov-15 | RTA | 29 | miner | S | Austinmer | Austinmer | |
| OWENS, Richard | Corrimal | ||||||||||
| OXMAN, F | Keiraville | ||||||||||
| 5798 | Mining Corps | OXMAN, George | Sapper | 27-Mar-16 | 11/05/19 | 30 | miner | M | Keiraville | Wollongong, WC | |
| 5799 | Mining Corps | OXMAN, John Henry | Sapper | 27-Mar-16 | 11/05/19 | 28 | miner | M | Keiraville | ||
| 4092 | 30 Bn | OYSTON, Thomas | Private | 19-Jun-16 | 5/07/19 | 19 | draper | S | Dapto | Dapto RSL, Dapto C/E | |
| 729 | 1 Bn | OYSTON, William | Private | 28 Aug 1914 | 5/07/15 | 22 | railway employee | S | Dapto | Dapto RSL, Dapto C/E, Wollongong |