Green Line C branch

The C branch, also called the Beacon Street Line or Cleveland Circle Line, is one of four branches of the Massachusetts Bay Transportation Authority's Green Line light rail system in the Boston, Massachusetts metropolitan area. The line begins at Cleveland Circle in the Brighton neighborhood of Boston and runs on the surface through Brookline along the median of Beacon Street. Reentering Boston, the line goes underground through the St. Mary's Street incline and joins the B and D branches at Kenmore. Trains run through the Boylston Street subway to Copley where the E branch joins, then continue through the Tremont Street subway to downtown Boston. The C branch has terminated at Government Center station since October 2021.

As of February 2023, service operates on 7 to 8-minute headways at weekday peak hours and 10 to 11-minute headways at other times, using 8 to 11 trains (16 to 22 light rail vehicles).