The BMT Fourth Avenue Line is a rapid transit line in Brooklyn, New York City, operated by the Brooklyn-Manhattan Transit Corporation. It runs primarily along Fourth Avenue, connecting several neighborhoods and providing access to various subway lines. The line features both elevated and underground sections, with key stations including Bay Ridge, Sunset Park, and Park Slope. It serves as an important transportation route for commuters and residents, linking to the BMT Sea Beach Line and the IND Culver Line at various points along its route.