- Oceanside
- Oceanview
- Ocosta
- Odair
- Officers Row
- Offutt Lake
- Ohlers Island
- Ohop
- Ohop Bob
- Oil City
- Olalla
- Old Royal
- Old Tacoma
- Old Toroda
- Old Town
- Old Wauconda
- Olds
- Olema
- Olequa
- Olga
- Olympic Hot Springs
- Olympic View
- Olympic View Mobile Home Park
- Olympic View Mobile Manor
- Omans
- Onalaska
- One Hawkeye Mobile Home Park
- One Hundred Thirty - Eighth Park Mobile Estates
- Oneida
- Onion Creek