The SEPTA Main Line is the section of the SEPTA Regional Rail system from the Zoo Interlocking in West Philadelphia to Lansdale Station in Lansdale, Pennsylvania. The line is 26.25 miles (42.25 km) long, and serves all 13 SEPTA Regional Rail lines.

The SEPTA Regional Rail system is a commuter rail network owned by SEPTA and serving the Philadelphia metropolitan area. The system has 13 branches and more than 150 active stations in Philadelphia, Pennsylvania, its suburbs and satellite towns and cities. It is the sixth-busiest commuter railroad in the United States, and the busiest outside of the New York, Chicago, and Boston metropolitan areas. In 2016, the Regional Rail system had an average of 132,000 daily riders and 118,800 daily riders as of 2019.