IMO or Imo may refer to:
- IMO (in my opinion), an Internet slang expression
- IMO number, a unique identity number issued to seacraft (pattern "1234567")
- Imo State, Nigeria
- Icelandic Meteorological Office
- Intelligent Medical Objects, a privately held company specializing in medical vocabularies
- International Maritime Organization
- International Mathematical Olympiad
- International Meteor Organization
- International Meteorological Organization
- Irish Medical Organisation, the main organization for doctors in the Republic of Ireland
- Isomaltooligosaccharide, a mixture of short-chain carbohydrates which has a digestion-resistant property
- SS Imo, a 1889 ship involved in the Halifax Explosion
- Idiopathic Massive Osteolysis, a name for Gorham's disease