| Firebase O'Reilly | |
|---|---|
| Coordinates | 16°30′21″N 107°10′19″E / 16.5057°N 107.172°E |
| Type | Army |
| Site information | |
| Condition | abandoned |
| Site history | |
| Built | 1968 |
| In use | 1968-70 |
| Battles/wars |  Vietnam War |
| Garrison information | |
| Occupants | 1st Division (South Vietnam) |
Firebase O'Reilly (also known as Hill 542) is a former Army of the Republic of Vietnam (ARVN) firebase located south of Quảng Trị in Quảng Trị Province, Vietnam.