MNO is an abbreviation for mobile network operator. It may also refer to

• Manganese oxide (MnO)
• 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