| Name of place | Number of counties | Principal county | Lower zip code | Upper zip code |
|---|---|---|---|---|
| Ohogamiut | 1 | Wade Hampton Census Area | ||
| Old Anderafski | 1 | Wade Hampton Census Area | 99658 | |
| Old Chatanika | 1 | Fairbanks North Star Borough | ||
| Old Harbor | 1 | Kodiak Island Borough | 99643 | |
| Old Kvichak | 1 | Dillingham Census Area | ||
| Old Minto | 1 | Yukon-Koyukuk Census Area | ||
| Old Ninilchik | 1 | Kenai Peninsula Borough | ||
| Old Rampart | 1 | Yukon-Koyukuk Census Area | ||
| Old Tyonek | 1 | Kenai Peninsula Borough | 99682 | |
| Old Valdez | 1 | Valdez-Cordova Census Area | ||
| Olive Cove | 1 | Wrangell-Petersburg Census Area | ||
| Olnes | 1 | Fairbanks North Star Borough | 99701 | |
| Ophir | 1 | Yukon-Koyukuk Census Area | ||
| Orca | 1 | Valdez-Cordova Census Area | 99574 | |
| Oscarville | 1 | Bethel Census Area | 99559 | |
| Oskawalik | 1 | Bethel Census Area | ||
| Outer Ketchikan | 1 | Prince of Wales-Outer Census Area | ||
| Ouzinkie | 1 | Kodiak Island Borough | 99644 | |