Canada
Countries of the world
O
- (Capitale-Nationale) Orleans Island (historical)
- (Sunshine Coast Regional District) Oyster Island
- (Capital Regional District) Owl Island
- (Regional District of Mount Waddington) Owl Island
- (Regional District of Alberni-Clayoquot) Owens Island
- (Capital Regional District) Owen Island
- (Charlotte County) Oven Head Island
- (Central Coast Regional District) Oval Island
- (Charlotte County) Outer Wood Island
- (Manitoulin District) Outer Duck Island
- (Powell River Regional District) Otter Island
- (Regional District of Alberni-Clayoquot) Ottaway Islet
- (Regional District of Alberni-Clayoquot) Onion Island
- (Skeena-Queen Charlotte Regional District) Orwig Islets
- (Regional District of Mount Waddington) Onetree Islet
- (Central Coast Regional District) O'Neil Islet
- (Powell River Regional District) Olsen Island
- (Strathcona Regional District) O'Leary Islets
- (Regional District of Mount Waddington) Olden Island
- (Central Coast Regional District) Oland Islet
- (Skeena-Queen Charlotte Regional District) Ogilvie Island
- (Central Coast Regional District) Odlum Island
- (Charlotte County) Odell Island
- (Regional District of Alberni-Clayoquot) Ocayu Island
- (Regional District of Alberni-Clayoquot) Obstruction Island
- (Regional District of Kitimat-Stikine) Observation Islet
- (Central Coast Regional District) Oblong Island