MDD

MDD may refer to:


 * Major depressive disorder, a mental disorder involving persistent low mood, low self-esteem and loss of interest. It is also known as clinical depression.
 * Mate-Demate Device, a specialized crane used to piggyback the Space Shuttle onto an airplane
 * Mammal Diversity Database, online checklist of mammal species maintained by the American Society of Mammalogists
 * Medical Devices Directive
 * Mernda railway station, Melbourne
 * Midland Airpark (IATA: MDD), a public use airport in Midland, Texas
 * Mine detection dogs
 * Ministry of Defence (Italy), known natively as Ministero della Difesa
 * Mirrored Drive Door, a case design for the Power Mac G4
 * Model-driven development, a software engineering discipline