MDI may stand for:
- Management Development Institute,Gurgaon,India: An elite Business School of India. Others in the ivy league include the [[IIM]]s,FMS, [[NIA SoM]], XLRI and IIFT.
- Multiple document interface
- the chemical compound methylene diphenyl 4,4'-diisocyanate or shorter 4,4'-MDI
- medium dependent interface
- metered dose inhaler, a device for administering a puff of medication into the lungs, such as for asthma
- Moteur Developpment International developer of a compressed air engine