MBTA subway

The Massachusetts Bay Transportation Authority (MBTA) operates rapid transit (heavy rail), light rail, and bus rapid transit services in the Boston metropolitan area, collectively referred to as the rapid transit, subway, or the T.

The color-branded lines consist of three heavy rail lines (Red, Orange, and Blue), one branched light rail system (Green), and a short light rail line (the Mattapan Line, colored as part of the Red Line). All except the Ashmont–Mattapan line operate in tunnels in the downtown area, but no route operates entirely underground, and only 31 out of the system's 153 stations are located underground. The five branches of the Silver Line bus network are also shown as part of the rapid transit system. Three branches operate underground and charge rapid transit fares; two branches operate entirely on the surface and charge lower bus fares.

In 2025, the heavy rail lines had 101,054,600 rides, or about 326,500 per weekday in the first quarter of 2026, and comprised the fourth-busiest heavy rail system in the United States. In the same period, the light rail lines had 42,065,000 rides, or about 124,900 per weekday, and comprised the third-busiest light rail system in the United States.

The section of the Tremont Street subway between Park Street and Boylston Street stations, now on the Green Line, opened in 1897, making it the oldest transit subway in North America still in use (preceded only by the short-lived Beach Pneumatic Transit demonstration line in New York City).