IMO

The three-letter abbreviation IMO may have several meanings, depending on context:
* Idiopathic Massive Osteolysis (Gorham's Disease)
* In Memory Of
* In my opinion – Internet slang
* Independent Market Operator of Ontario, Canada (now the Independent Electricity System Operator (IESO))
* Instituto de la Mujer Oaxaqueña
* Intermediate Mathematical Olympiad, a challenge for students aged 11-16 organized by the United Kingdom Mathematics Trust
* International Maritime Organization
* International Mathematical Olympiad
* International Meteor Organization
* International Meteorological Organization
* International money order
* International Muslims Organization
* Irish Medical Organisation (a labor union)

The word ‘Imo’, of which only the first letter is capital, may also refer to:
* A Japanese language slur equivalent to "country bumpkin" (Lit. Potato)
* Imo State, Nigeria
* The World War I-era Belgian-Relief ship "Imo" involved in a collision with the French munitions ship "Mont Blanc" in Halifax Harbour, Nova Scotia, Canada, the result of which caused the Halifax Explosion.