List of geography topics (O)

:O'Higgins Glacier – :O'Higgins Lake – :O'Sullivans Cascade – :Oak Harbor, Washington – :Oak Harbor Marina – :Oakland, California – :Ob River – :Obbola Bridge – :Oberaletsch Glacier – :Oberalp Pass – :Oberbaumbrücke – :Oberer Glacier – :Oberhalbstein Range – :Oblast – :Occupation of the Gaza Strip by Egypt – :Ocean – :Ocean current – :Oceania – :Oceanography – :October 16 – :Oder – :Oder-Havel Canal – :Oder River – :Odsherred – :Ofothalvøya – :Oga-hanto – :Ogilvie Mountains – :Ohanapecosh Glacier – :Ohio River – :Okanagan Highland – :Okavango River – :Oklahoma – :Okres – :Okrug – :Okstindbreen – :Old Blewett Pass – :Old Bridge, Svilengrad – :Old Faithful Geyser – :Old Mission Peninsula – :Old World – :Olo'upena Falls – :Oltenia – :Oltenian Sahara – :Olympia, Washington – :Olympic Mountains – :Olympic Peninsula – :Oman – :One-China policy – :One Tree Hill, New Zealand – :One country, two systems – :Onelli Glacier – :Ontario – :Opawskie Mountains – :Opština – :Oquirrh Mountains – :Orakei Korako – :Orange River – :Orbetello – :Orchard – :Ord River – :Ordos Desert – :Oregon – :Oresund – :Oresund Bridge – :Organ Mountains – :Organic Act – :Organization of the Islamic Conference – :Organized territory – :Orinoco River – :Orkhon River – :Orlicke Mountains – :Orlov Most – :Orthographic projection (cartography) – :Ortiz Mountains – :Ortler Alps – :Oruro – :Osa Peninsula – :Osaka – :Oshika-hanto – :Oslo Accords – :Osmore River – :Osorno – :Osten Transporter Bridge – :Ostān – :Osumi Peninsula – :Otago Peninsula – :Otava river – :Otemma Glacier – :Otero County, New Mexico – :Other – :Otira – :Ottawa – :Ouachita Mountains – :Oude A-vaart – :Oude Maas – :Ounceland – :Ourthe Canal – :Outlet glacier – :Ouzoud Falls – :Ovens River – :Overpopulation – :Owen Bank – :Owen Bank (Seychelles) – :Owen Sound, Ontario – :Owen Stanley Range – :Owl Creek Mountains – :Owl Mountains – :Oxbow lake – :Oxgang – :Oxygen – :Ozark Mountains –