Line A may refer to:

• A (Los Angeles Railway), a former streetcar service in California, United States
• A (New York City Subway service), in New York, United States
• Line A (Buenos Aires Underground), in Argentina
• Line A (Prague Metro), in the Czech Republic
• Line A (Rome Metro), in Italy
• Mexico City Metro Line A, in Mexico
• Santiago Metro Line A, a planned line in Chile
• Bilbao tram, in Bilbao, Spain, originally called Line A

• A Line (disambiguation)
• A Train (disambiguation)