The Silver Line is a system of bus routes in Boston and Chelsea, Massachusetts, operated by the Massachusetts Bay Transportation Authority (MBTA). It is operated as part of the MBTA bus system, but branded as bus rapid transit (BRT) as part of the MBTA subway system. Six routes are operated as part of two disconnected corridors. As of 2019, weekday ridership on the Silver Line was 39,000.

Chelsea is a city in Suffolk County, Massachusetts, United States, directly across the Mystic River from Boston. At the 2020 census, Chelsea had a population of 40,787, making it the second most densely populated city in Massachusetts, behind Somerville. With a total area of 2.46 square miles (6.4 km2), Chelsea is the smallest city in Massachusetts in terms of total area. It is the city with the second-highest percentage of Latino residents in Massachusetts, behind Lawrence.