IMO or Imo may refer to:

• International Maritime Organization
  • IMO number, a unique identity number issued to seacraft (pattern "1234567")
• SS Imo, a 1889 ship involved in the Halifax Explosion

• International Meteorological Organization
• Icelandic Meteorological Office

• Irish Medical Organisation, the main organisation representing doctors in Ireland
• Intelligent Medical Objects, a privately held company specializing in medical vocabularies
• Isomaltooligosaccharide, a mixture of short-chain carbohydrates which has a digestion-resistant property
• Idiopathic Massive Osteolysis, a name for Gorham's disease, a rare bone disease
• International Mathematical Olympiad
• International Meteor Organization
• Imo State, Nigeria
• imo.im, a video calling and instant messaging app
• IMO (in my opinion), an Internet slang expression