The Northeast Corridor (commonly abbreviated as the NEC) is a fully electrified railway line owned primarily by Amtrak serving the Northeast megalopolis of the United States from Boston in the north, via New York to Washington, D.C. in the south, with branches serving other cities. The line is used by the Acela Express and the Northeast Regional between New York and Washington plus other Amtrak routes in addition to commuter rail services and freight rail transport.

The NEC, which closely parallels Interstate 95 for most of its length, is the busiest passenger rail line in the United States by ridership and service frequency. The Acela Express, which entered service in 2000, is the only true high speed rail in North America and operates at speeds up to 150 mph (241 km/h), taking 2 hours 48 minutes between New York and Washington; for the rest of the route, however, speed is limited to 135 mph (217 km/h). Plans have been prepared for a $117-billion (2010 dollars) project to reduce the Boston-Washington time to 180 minutes, New York–Washington time to 96 minutes and Boston–New York to 84 minutes.