MDN may refer to:
Computing and technology MDN Web Docs (formerly Mozilla Developer Network), a Mozilla website for developer documentation Message Disposition Notification, a form of return receipt for e-mail Telephone number for mobile devices, as in: Mobile device number Mobile dialable number Mobile directory number
Organizations Ministry of National Defence (Portugal) (Ministério da Defesa Nacional), the Portuguese defence ministry Nicaraguan Democratic Movement (Movimiento Demócratico Nicaragüense)
Transport Macedon railway station, Victoria, Australia (station code: MDN) Madison Municipal Airport (Indiana), Madison, Indiana, United States (IATA code: MDN) Maiden Newton railway station, England (National Rail station code: MDN) Medan railway station, North Sumatra, Indonesia (station code: MDN) Meriden (Amtrak station), Connecticut, United States (Amtrak station code: MDN) Milwaukee District North Line, a rail line in Chicago, Illinois, US Minggang East railway station, China (China Railway telegraph code: MDN) Morden tube station (London Underground station code: MDN) Mudan Airlines, Somali Republic (ICAO code: MDN)
Other uses East German mark (Mark der Deutschen Notenbank), the official unit of currency in East Germany from 1964 to 1967 Maya Day Number, the sum of days in Mesoamerican Long Count calendar Mbati language (ISO 639-3: mdn) MdN Interactive, the magazine for Macintosh designers Network MDN, a television station in Griffith, New South Wales, and sister station of MTN