The Blue Line is one of the four subway lines of the Massachusetts Bay Transportation Authority. It extends from Wonderland Station in Revere in the north to Bowdoin Street near Beacon Hill in Boston in the south. It meets the Green Line at Government Center and the Orange Line at State Street. It also provides mass-transit service to Logan International Airport. The line is designated "Blue" because for much of its length it uses the old Boston, Revere Beach & Lynn Railroad right-of-way along the seacoast in Revere and East Boston, and the tunnel to East Boston runs under water.

Blue Line cars are unique among rapid transit vehicles in Boston in that they use both third rail and overhead pantograph current pickup. The line switches between the two at the Logan Airport station where it transitions between running in a tunnel and running above ground. These cars are also shorter than otherwise similar ones running on the Orange Line, as the Blue Line (known as the East Boston Tunnel before the MBTA was formed) was initially designed to carry streetcars. The subway portion of the line was retrofitted with raised station platforms and urban heavy rail cars in the 1920s, with the surface portion between East Boston and Revere (known pre-MBTA as the East Boston Extension) added in the 1950s.

There is currently (2005) a proposal to extend the Blue Line northward to reach as far as Salem, Massachusetts; the land to extend the line was purchased during initial construction, but due to budgetary constraints, Wonderland was designated the northern terminus. There is also a plan to extend the line's southern end west to Charles/MGH, where it would connect with the Red Line. This was one of the mitigation measures the Commonwealth of Massachusetts agreed to as part of the Big Dig.

Stations

• Bowdoin
• Government Center
• State
• Aquarium
• Maverick
• Airport
• Wood Island
• Orient Heights
• Suffolk Downs
• Beachmont
• Revere Beach
• Wonderland

Accessibility

The Blue Line is accessible except for the most important stations: those downtown. Currently, the outbound Blue Line platform at State Street is wheelchair accessible to the street. Inbound wheelchair users can take the Blue Line to Government Center and cross the platform there to an outbound Blue Line train and take it to the accessible State Street platform. The MBTA has plans to make the remaining Blue Line stations accessible as part of a larger effort to permit 6 car trains on the line. See MBTA accessibility.