- Otis
- Oak Ridge
- Ocean Point
- Olivers Island
- Old Mill Mobile Home Park
- Orangeport
- Otter Lake
- Oak Orchard
- Onativia
- Onondaga Castle
- Onondaga Hill
- Oot Park
- Oran
- Orchard Village
- Oswego Bitter
- Otisco
- Otisco Valley
- Orleans
- Oak Ridge Park
- Old Orchard Trailer Park
- Orange Lake Mobile Home Park
- Orrs Mill
- Otter Kill
- Otter Kill Estates
- Overlook Estates
- Oxford
- Oak Orchard
- Oak Orchard Estates
- Orchard Mobile Home Park
- Oswego Beach