The Providence/Stoughton Line is an MBTA Commuter Rail service in Massachusetts and Rhode Island, primarily serving the southwestern suburbs of Boston. Most service runs entirely on the Northeast Corridor between South Station in Boston and Providence station or Wickford Junction station in Rhode Island, while the Stoughton Branch splits at Canton Junction and terminates at Stoughton. It is the longest MBTA Commuter Rail line, and the only one that operates outside Massachusetts. The line is the busiest on the MBTA Commuter Rail system, with 17,648 daily boardings in an October 2022 count.

The MBTA Commuter Rail system serves as the commuter rail arm of the Massachusetts Bay Transportation Authority's (MBTA's) transportation coverage of Greater Boston in the United States. Trains run over 394 mi (634 km) of track to 134 stations. It is operated under contract by Keolis, which took over operations on July 1, 2014, from the Massachusetts Bay Commuter Railroad Company (MBCR).