O
- (Sitka City and Borough) Obsechki Island
- (Thomas County) Observation Island
- (Ketchikan Gateway Borough) Observation Rock
- (Sitka City and Borough) Onetree Rock
- (Thomas County) Onslow Island
- (Prince of Wales-Hyder Census Area) Orr Island
- (Ketchikan Gateway Borough) Osten Island
- (Yakutat City and Borough) Otmeloi Island
- (Sitka City and Borough) Otstoia Island
- (Sitka City and Borough) Oval Rock
- (Prince of Wales-Hyder Census Area) Owl Island
- (Yakutat City and Borough) Osier Island
- (Yukon-Koyukuk Census Area) Oyle Island
- (Lowndes County) Oarlock Island
- (Aleutians West Census Area) Ogangen Island
- (Campbell County) Operl Island
- (Kusilvak Census Area) Olor Island
- (Greene County) Olsen Island
- (Campbell County) Olga Rock
- (Greene County) Old Valdez
- (Yukon-Koyukuk Census Area) Old Salmon Village
- (Yukon-Koyukuk Census Area) Old McGrath
- (Aleutians West Census Area) Old Man Rocks
- (Northwest Arctic Borough) Old Kotzebue
- (Lake and Peninsula Borough) Old Iliamna
- (Aleutians West Census Area) Ogchul Island
- (Aleutians West Census Area) Oglodak Island
- (Aleutians West Census Area) Ogliuga Island
- (Greene County) Observation Island
- (Bethel Census Area) Oscarville