- Oak Grove
- Oak Island
- Oak Leaf
- Oak Point
- Oak Ridge
- Oak Ridge
- Oak Ridge North
- Oak Trail Shores
- Oak Valley
- Oakalla
- Oakhurst
- Oakwood
- Oatmeal
- O'brien
- Odem
- Odessa
- Oglesby
- Old River
- Old River-Winfree
- Olivarez
- Olmos Park
- Olney
- Omaha
- Onalaska
- Orange
- Orange Grove
- Orange Grove-Sandia
- Orangefield
- Orchard
- Orchard-Kendleton
- Ore City
- Ovalo
- Overton
- Ovilla
- Oyster Creek
- Ozona