MCI or mci may refer to:
Organizations Companies MCI Communications, originally Microwave Communications Inc., a corporation that operated as MCI from 1963 to 1998 MCI Inc., formerly called WorldCom, which acquired MCI Communications, and was later acquired by Verizon Communications MCI (recording studio gear), a manufacturer of multi-track audio tape recorders and mixing consoles for professional studio recording (officially Music Center Incorporated, later Music Consultants Incorporated) Mobile Telecommunication Company of Iran, the largest mobile phone operator in Iran Motor Coach Industries, a coach/bus manufacturing company Music Collection International, the music division of Video Collection International MCI, Frank Farian's record label
Education Maine Central Institute, a boarding school in Maine, United States Malvern Collegiate Institute, a secondary school in Toronto, Ontario, Canada Marine Corps Institute, a coursework of Marine Corps education and training programs Martingrove Collegiate Institute, a secondary school in Toronto, Ontario, Canada MCI Management Center Innsbruck, a privately organized business school in Innsbruck, Austria Medical Council of India, a former statutory body for establishing uniform and high standards of medical education in India Mennonite Collegiate Institute, a private religious school in Gretna, Southern Manitoba Middlefield Collegiate Institute, a secondary school in Markham, Ontario, Canada Museum Conservation Institute, of the Smithsonian Institution
Other organizations Ministry of Communications and Information, a ministry of the Government of Singapore Motek Cultural Initiative, a Toronto-based nonprofit organization promoting Israeli music and culture
Science and technology Millicurie (mCi), 1/1000 of a curie, a non-SI unit of radioactivity Megacurie (MCi), 1,000,000 times a curie, a non-SI unit of radioactivity Macroinvertebrate Community Index, an index where the presence or lack of macroinvertebrates is used for monitoring stream health in New Zealand Magnetic current imaging, using a scanning SQUID microscope Malicious caller identification, a type of enhanced telephone service Mass-casualty incident, a medical emergency involving more patients than can be easily handled by the crews initially assigned to the incident Media Control Interface, an API for controlling multimedia peripherals connected to a Microsoft Windows or OS/2 computer Meta-circular evaluator, in computing Methylchloroisothiazolinone, in chemistry Mild cognitive impairment, a neurological affliction often associated with Alzheimer's disease Modulation contrast imaging, a term related to optical transfer function
Art, entertainment, and media MasterChef Indonesia, an Indonesian televised cooking competition
Other uses 1101, in Roman numerals Kansas City International Airport (IATA code), Missouri, United States Meal, Combat, Individual ration, the successor to the U.S. Army C-ration Michigan City station (Amtrak code), Indiana, United States Miss Chinese International Pageant, an annual pageant for international women of Chinese descent Monetary conditions index, a macroeconomic index number relevant for monetary policy Manchester City F.C., abbreviated as MCI Mese language, an ISO 639-3 code Missing Children Incident, an event in the lore of Five Nights At Freddy's