O
- Oakdale
- Oakdene Point
- Oak Flats
- Oakgrove
- Oak Heights
- Oakhill Forest
- Oak Lake
- Oakland
- Oak Leaf
- Oak Orchard
- Oakridge
- Oak Ridges
- Oak Valley
- Oakview Beach
- Oakville
- Oakwood
- Oakwood-Vaughan
- Oatland
- Oba
- Obabikong Indian Reserve No. 35B
- Obadjiwan Indian Reserve No. 15E
- Obakami
- O'Brien
- O'Briens Landing
- O'Connell
- O'Connor
- O'Connor-Parkview
- Oconto
- Octopus
- O'Dell
- Odena
- Odenback
- Odessa
- O'Donnell Landing
- Off Lake Corner
- Ogahalla
- Ogaki
- Ogden's Beach
- Ogidaki
- Ogoki
- O'Grady Settlement
- Ohsweken
- Oil City
- Oil Springs
- Oja
- Ojibway
- Ojibway Island
- Ojibway Nation of Saugeen Indian Reserve
- Olcott
- Oldcastle
- Old Cut
- Old East York
- Oldfield
- Old Fort
- Old Glenridge
- Old Killaloe
- Old Mine Centre
- Old Road Crossing
- Old Spring Bay
- Old Stittsville
- Old Woman's River
- Olinda
- Oliphant
- Oliver
- Oliver Paipoonge
- Olivet
- Omagh
- Ombabika
- Omeedjilawh Camp
- Omemee
- Ompah
- Onagon
- Onakawana
- Onaping
- Onaping Dam
- Onaping Falls
- Oneida 41
- One Man Lake Indian Reserve No. 29
- Onondaga
- Opasatika
- Opasquia
- Opemisha
- Opeongo
- Opeongo Line
- Ophir
- Orange Corners
- Orangeville
- Oranmore
- Orchard Beach
- Orchard Beach
- Orchard Grove
- Orchard Point
- Orchardside
- Orchardville
- O'Reilly's Bridge
- Oriel
- Orient
- Orient Bay
- Orillia
- Oriole Parkway
- Orkney Beach
- Orland
- Orléans
- Ormond
- Ormond Beach
- Ormsby
- Oro Beach
- Oro Lea Beach
- Oro-Medonte
- Orono
- Oro Park
- Oro Station
- Orr Lake
- Orrville
- Orton
- Orwell
- Osaca
- Osawin
- Osborne Corners
- Osceola
- Osgoode
- Oshawa
- Oskondaga
- Osnabruck Centre
- Osnaburgh 63A
- Osnaburgh 63B
- Osnaburgh House
- Ospringe
- Osseo
- Ossossane Beach
- Ostersund
- Ostrander
- Ostrom
- Ostryhon Corners
- Oswego Park
- Otonabee-South Monaghan
- Ottawa
- Otter Creek
- Otterdale
- Otter Lake
- Ottermere
- Otter Rapids
- Otterville
- Ouimet
- Oungah
- Oustic
- Outlet
- Outlook
- Ouvry
- Overflow
- Owakonze
- Owenbrook
- Owen Sound
- Oxbow Park
- Oxdrift
- Oxenden
- Oxford Centre
- Oxford Mills
- Oxford Station
- Oxley
- Oxmead
- Oxtongue Lake
- Ozone
