Barrios de Missouri O
- O'Fallon St Charles (50)
- Oak Meyer Gardens (3)
- Oak Park Northwest (6)
- Oak Park Southeast (9)
- Oak Park Southwest (9)
- Oak Tree Farm (2)
- Oaks Ridge Meadows (1)
- Oakville (6)
- Old Westport (6)
- Oldham Farms (4)
- Ott-Chrisman (7)
- Outer North Springfield (35)
- Outer Southeast Springfield (42)
- Outer Southwest Springfield (87)