World Factbook
Oahu (island)
Ocean Island (Banaba)
Oesterreich (local name for Austria)
Oil Islands (Chagos Archipelago)
Okhotsk, Sea of
Okinawa (island group)
Oland (island)
Oman, Gulf of
Oran (city)
Orange River Colony (region; former name of Free State Province of South Africa)
Oranjestad (capital)
Oresund (The Sound) (strait)
Orkney Islands
Oslo (capital)
Ottawa (capital)
Ouagadougou (capital)
Outer Mongolia (region)