Line C is a line designation used by several public transport systems:

United States C (AC Transit), a bus route in the San Francisco Bay Area, California, C (Los Angeles Railway), former streetcar service In Los Angeles, California C (New York City Subway service), a subway route in New York City, New York C Line (Los Angeles Metro), a light rail line in Los Angeles County, California C Line (RTD), a light rail line in Denver, Colorado Avenue C Line (Manhattan), a bus route in New York City, New York Metro C Line (Minnesota), a rapid bus route in Minneapolis, Minnesota RapidRide C Line, a bus route in Seattle, Washington

Elsewhere C (S-train), a commuter rail line in Copenhagen, Denmark Line C (Buenos Aires Underground), a metro line in Buenos Aires, Argentina Line C (Prague Metro), a metro line in Prague, Czech Republic Line C (Rome Metro), a metro line in Rome, Italy Bordeaux Tramway line C, a tram route in Bordeaux, France Lyon Metro Line C, a metro line in Lyon, France RER C, a commuter rail line in Paris, France

See also C Train (disambiguation)