MNO is an abbreviation for mobile network operator. It may also refer to Manganese oxide (MnO) Métis Nation of Ontario in Canada Ministry of Defence in some Slavic-speaking countries: Ministry of Defence (Czechoslovakia) Ministry of Defence of the Slovak State Multinational organization Manono Airport (IATA airport code MNO) in Manono, Democratic Republic of the Congo Master of Nonprofit Organizations, a graduate-level degree