This page is about the cancelled highway near Boston, Massachusetts. For the future light rail project in Minneapolis, Minnesota, see Southwest Corridor (Minnesota).

The Southwest Corridor or Southwest Expressway was a project designed to bring an eight-lane highway into the City of Boston from a direction southwesterly of downtown. It was supposed to connect with Interstate 95 (I-95) at Route 128. As originally designed, it would have followed the right of way of the former Penn Central/New Haven Railroad mainline (current Amtrak Northeast Corridor) running from Readville, north through Roslindale, Forest Hills and Jamaica Plain, where it would have met the also-cancelled I-695 (Inner Belt Expressway). The 50-foot-wide (15 m) median for the uncompleted "Southwest Expressway" would have carried the southwest stretch of the MBTA Orange Line within it, replacing the Washington Street Elevated railway's 1901/1909-built elevated railbed.