The Red Line is a rapid transit line operated by the Massachusetts Bay Transportation Authority (MBTA) as part of the MBTA subway system. The line runs south and east underground from Alewife station in North Cambridge through Somerville and Cambridge, surfacing to cross the Longfellow Bridge then returning to tunnels under Downtown Boston. It continues underground through South Boston, splitting into two branches on the surface at JFK/UMass station. The Ashmont branch runs southwest through Dorchester to Ashmont station, where the connecting light rail Ashmont–Mattapan High Speed Line continues to Mattapan station. The Braintree branch runs southeast through Quincy and Braintree to Braintree station.

Ashmont station is a Massachusetts Bay Transportation Authority (MBTA) intermodal transit station located at Peabody Square in the Dorchester neighborhood of Boston, Massachusetts. It is the southern terminus of the Ashmont branch of the rapid transit Red Line, the northern terminus of the connecting light rail Ashmont–Mattapan High-Speed Line, and a major terminal for MBTA bus service. Ashmont has two side platforms serving the below-grade Red Line and a single side platform on an elevated balloon loop for the Mattapan Line. The station is fully accessible for all modes.