MARC standards, a data format used for library cataloging,
MARC Train, a regional commuter rail system of the State of Maryland, serving Maryland, Washington, D.C., and eastern West Virginia
MARC (archive), a computer-related mailing list archive
M/A/R/C Research, a marketing research and consulting firm
Massachusetts Animal Rights Coalition, a non-profit, volunteer organization
Matador Automatic Radar Control, a guidance system for the Martin MGM-1 Matador cruise missile
Mid-America Regional Council, the Council of Governments and the Metropolitan Planning Organization for the bistate Kansas City region
Midwest Association for Race Cars, a former American stock car racing organization
Revolutionary Agrarian Movement of the Bolivian Peasantry (Movimiento Agrario Revolucionario del Campesinado Boliviano), a defunct right-wing political movement
Mid-Atlantic Rowing Conference, a college rowing conference.
Other uses
Marc is the French word for pomace, fruit solids as used for making pomace brandy
Marz, Austria, aka Márc, a town
Marc (cycling team), a Belgian road-racing team 1978–1980
Marc (TV series), a pop music television show presented by Marc Bolan
MSC Marc, a finite element analysis software
MARC Cars Australia, an Australian motor racing team and manufacturer
Various related obsolete units of weight - see Apothecaries' system