- Oneida Village Mobile Home Park
- Oneonta
- Oniontown
- Oniontown
- Onondaga Castle
- Onondaga Hill
- Onoville
- Ontario
- Ontario Beach
- Ontario Center
- Ontario on the Lake
- Onteo Beach
- Onteora Park
- Oot Park
- Oppenheim
- Oramel
- Oran
- Orange Lake
- Orange Lake Mobile Home Park
- Orangeburg
- Orangeburg, Saratoga
- Orangeport
- Orangeville Center
- Orchard Grove Village Park
- Orchard Knoll
- Orchard Mobile Home Park
- Orchard Park
- Orchard Park
- Orchard Terrace
- Orchard Village