| Ollie Branch | rises in central Graham County and flows SW into East Buffalo Creek. |
| Olmmetta | community in E Wilkes County. |
| Olne | community in NW Warren County served by post office, 1886-1904. |
| Olympia | community in W Pamlico County. In 1891 named for Mount Olympus when a post office, discontinued in 1908, was est. there. |
| Omega | community in N Rowan County served by post office, 1886-1904. |
| Oneida | community in N Alamance County served by post office, 1900-1908. |
| Onetree Point | shown on Moseley map, 1733, extending from the mainland of what is now SE Brunswick County into Cape Fear River between Elizabeth River and Walden Creek. Located N of and adjacent to Deep Water Point. Not shown on modern maps. |
| Onion Falls | in West Fork Tuckasegee River at the N end of Thorpe Reservoir in W Jackson County. |
| Onion Knob | Alexander-Wilkes county line. |
| Onion Mountain | E Macon County between the head of Cat Creek and Laurel Creek. Alt. 3,500. |