The Northeast megalopolis, also known as the Northeast Corridor, Acela Corridor, Boston–Washington corridor, BosWash, or BosNYWash, is the world's largest megalopolis by economic output and the most populous megalopolis exclusively within the United States, with about 50 million residents as of 2022.

A megalopolis or a supercity, also called a megaregion, is a group of metropolitan areas which are perceived as a continuous urban area through common systems of transport, economy, resources, ecology, and so on. They are integrated enough that coordinating policy is valuable, although the constituent metropolises keep their individual identities. The megalopolis concept has become highly influential as it introduced a new, larger scale thinking about urban patterns and growth.