- Ocean Springs, Mississippi
- Ocean Township, New Jersey
- Ocoee, Tennessee
- Odenville, Alabama
- Odessa, Missouri
- Odessa, Texas
- Ogden, Iowa
- Ojai, California
- Okemos, Michigan
- Oklahoma City, Oklahoma
- Olathe, Kansas
- Old Fort, Tennessee
- Old Greenwich, Connecticut
- Old Hickory, Tennessee
- Old Westbury, New York
- Olmsted Falls, Ohio
- Olympic Valley, California
- Omaha, Nebraska
- Ooltewah, Tennessee
- Opelika, Alabama
- Orange, Connecticut
- Oregonia, Ohio
- Orem, Utah
- Orient, New York
- Orinda, California
- Orlando, Florida
- Ormond Beach, Florida
- Oro-Medonte, Ontario
- Orono, Maine
- Ortonville, Michigan
- Ossining, New York
- Ostrander, Ohio
- Oswego, New York
- Otis, Oregon
- Overland Park, Kansas
- Oviedo, Florida
- Owasso, Oklahoma
- Owensboro, Kentucky
- Oxford, Florida
- Oxford, Georgia
