| Name | What | Region | Country | Lat | Long | Elev ft. | Pop est |
|---|---|---|---|---|---|---|---|
| O'Brien | city | Washington | United States | 47.41 | -122.24 | 190 | |
| Oak Acres Mobile Home Park | city | Washington | United States | 47.00 | -123.46 | 91 | |
| Oak Harbor | city | Washington | United States | 48.29 | -122.64 | 0 | |
| Oak Hollow Mobile Home Park | city | Washington | United States | 48.31 | -122.65 | 98 | |
| Oak Park | city | Washington | United States | 45.58 | -122.39 | 108 | |
| Oak Point | city | Washington | United States | 46.19 | -123.19 | 246 | |
| Oakesdale | city | Washington | United States | 47.13 | -117.24 | 2536 | |
| Oakland | city | Washington | United States | 47.23 | -122.49 | 308 | |
| Oakland | city | Washington | United States | 47.23 | -123.07 | 3 | |
| Oaknoll Trailer Park | city | Washington | United States | 47.16 | -122.48 | 298 | |
| Oakridge Manor Mobile Home Park | city | Washington | United States | 47.04 | -122.38 | 830 | |
| Oaks Mobile Home Park | city | Washington | United States | 48.50 | -123.04 | 111 | |
| Oakville | city | Washington | United States | 46.84 | -123.23 | 200 | |
| Ocean Bay Mobile Home Park | city | Washington | United States | 46.49 | -124.04 | 29 | |
| Ocean City | city | Washington | United States | 47.07 | -124.17 | 39 | |
| Ocean Grove | city | Washington | United States | 47.18 | -124.20 | 0 | |
| Ocean Park | city | Washington | United States | 46.49 | -124.05 | 45 | |
| Ocean Shores | city | Washington | United States | 46.97 | -124.16 | 16 | |
| Ocean View Mobile Home Park | city | Washington | United States | 48.13 | -123.50 | 137 | |
| Oceanside | city | Washington | United States | 46.41 | -124.05 | 19 | |
| Oceanview | city | Washington | United States | 46.32 | -124.06 | 16 | |
| Ocosta | city | Washington | United States | 46.89 | -124.04 | 16 | |
| Odair | city | Washington | United States | 47.61 | -119.27 | 1761 | |
| Odessa | city | Washington | United States | 47.33 | -118.69 | 1669 | |
| Officers Row | city | Washington | United States | 45.63 | -122.66 | 39 | |
| Offutt Lake | city | Washington | United States | 46.91 | -122.83 | 347 | |
| Ohana Estates Mobile Home Park | city | Washington | United States | 47.18 | -122.42 | 400 | |
| Ohop | city | Washington | United States | 46.95 | -122.19 | 1669 | |
| Ohop Bob | city | Washington | United States | 46.87 | -122.34 | 830 | |
| Oil City | city | Washington | United States | 47.75 | -124.43 | 141 | |
| Okanogan | city | Washington | United States | 48.36 | -119.58 | 1046 | |
| Okanogan City (historical) | city | Washington | United States | 47.64 | -120.00 | 2509 | |
| Olalla | city | Washington | United States | 47.43 | -122.55 | 259 | |
| Old Royal | city | Washington | United States | 48.18 | -124.46 | 200 | |
| Old Tacoma | city | Washington | United States | 47.28 | -122.47 | 164 | |
| Old Toroda | city | Washington | United States | 48.78 | -118.91 | 3628 | |
| Old Town | city | Washington | United States | 48.15 | -123.15 | 26 | |
| Old Wauconda | city | Washington | United States | 48.71 | -118.95 | 4189 | |
| Olds | city | Washington | United States | 47.46 | -120.33 | 830 | |
| Olema | city | Washington | United States | 48.29 | -119.80 | 2020 | |
| Olequa | city | Washington | United States | 46.37 | -122.94 | 200 | |
| Olga | city | Washington | United States | 48.62 | -122.84 | 0 | |
| Olimpija | city | Washington | United States | 47.04 | -122.90 | 91 | |
| Olimpėjė | city | Washington | United States | 47.04 | -122.90 | 91 | |
| Olympia | city | Washington | United States | 47.04 | -122.90 | 91 | |
| Olympic Hills | city | Washington | United States | 47.73 | -122.30 | 200 | |
| Olympic Hot Springs | city | Washington | United States | 47.98 | -123.69 | 3349 | |
| Olympic View | city | Washington | United States | 47.69 | -122.74 | 236 | |
| Olympic View Mobile Home Park | city | Washington | United States | 48.20 | -122.68 | 95 | |
| Olympic View Mobile Manor | city | Washington | United States | 47.41 | -122.62 | 131 | |
| Omak | city | Washington | United States | 48.41 | -119.53 | 872 | |
| Omans | city | Washington | United States | 47.60 | -118.08 | 2509 | |
| Onalaska | city | Washington | United States | 46.58 | -122.72 | 830 | |
| One Hawkeye Mobile Home Park | city | Washington | United States | 48.09 | -122.82 | 196 | |
| One Hundred One Pines | city | Washington | United States | 47.31 | -122.04 | 830 | |
| One Hundred Thirty - Eighth Park Mobile Estates | city | Washington | United States | 47.13 | -122.45 | 328 | |
| Oneida | city | Washington | United States | 46.31 | -123.68 | 101 | |
| Onion Creek | city | Washington | United States | 48.78 | -117.81 | 2591 | |
| Onslow | city | Washington | United States | 47.17 | -124.11 | 85 | |
| Ophir | city | Washington | United States | 48.21 | -119.72 | 830 | |
| Opportunity | city | Washington | United States | 47.66 | -117.24 | 2076 | |
| Orcas | city | Washington | United States | 48.60 | -122.94 | 0 | |
| Orchard Avenue | city | Washington | United States | 47.68 | -117.30 | 1958 | |
| Orchard Bluff Mobile Home Park | city | Washington | United States | 47.52 | -122.64 | 298 | |
| Orchard Grove | city | Washington | United States | 47.39 | -122.02 | 400 | |
| Orchard Heights | city | Washington | United States | 47.53 | -122.60 | 298 | |
| Orchard Park | city | Washington | United States | 47.68 | -117.33 | 1948 | |
| Orchard Prairie | city | Washington | United States | 47.73 | -117.31 | 2509 | |
| Orchard Trailer Park | city | Washington | United States | 47.47 | -122.28 | 252 | |
| Orchards | city | Washington | United States | 45.67 | -122.56 | 200 | |
| Orient | city | Washington | United States | 48.87 | -118.20 | 1669 | |
| Orillia | city | Washington | United States | 47.44 | -122.25 | 193 | |
| Orin | city | Washington | United States | 48.49 | -117.91 | 1669 | |
| Orondo | city | Washington | United States | 47.63 | -120.23 | 830 | |
| Oroville | city | Washington | United States | 48.94 | -119.44 | 915 | |
| Orting | city | Washington | United States | 47.10 | -122.20 | 200 | |
| Osborn Corner | city | Washington | United States | 47.88 | -122.17 | 416 | |
| Osborne | city | Washington | United States | 47.90 | -119.06 | 1791 | |
| Osborne Corner | city | Washington | United States | 48.05 | -119.23 | 2598 | |
| Osceola | city | Washington | United States | 47.20 | -122.04 | 830 | |
| Oskams Corner | city | Washington | United States | 47.73 | -122.19 | 200 | |
| Oso | city | Washington | United States | 48.27 | -121.93 | 298 | |
| Ostrander | city | Washington | United States | 46.19 | -122.89 | 200 | |
| Otello | city | Washington | United States | 46.83 | -119.18 | 1099 | |
| Othello | city | Washington | United States | 46.83 | -119.18 | 1099 | |
| Otis Orchards | city | Washington | United States | 47.70 | -117.11 | 2040 | |
| Otis Orchards-East Farms | city | Washington | United States | 47.70 | -117.11 | 2040 | |
| Outlook | city | Washington | United States | 46.33 | -120.09 | 830 | |
| Overlake | city | Washington | United States | 47.64 | -122.14 | 200 | |
| Ovington | city | Washington | United States | 48.06 | -123.86 | 830 | |
| Oxley | city | Washington | United States | 46.62 | -122.91 | 400 | |
| Oyehut | city | Washington | United States | 47.02 | -124.16 | 3 | |
| Oysterville | city | Washington | United States | 46.55 | -124.03 | 0 | |
| Ozette | city | Washington | United States | 48.15 | -124.67 | 62 |