| Name |
Notability |
References |
| C. Y. O'Connor CMG |
Fremantle Harbour and the Goldfields Water Supply Scheme, Western Australia |
|
| Thomas Oakes |
Chief Engineer of the Schuylkill Canal |
|
| Tinius Olsen |
Norwegian American engineer and inventor, founder of the Tinius Olsen Engineering Testing Machine Company. |
|
| Rowland Mason Ordish |
designer of the St Pancras railway station arch roof |
|
| Ou Chin-der |
Taiwanese railway engineer and public official |
|
| Benjamin Outram |
canals |
|