The BNSF Line is a Metra commuter rail line operated by the BNSF Railway in Chicago and its western suburbs, running from Chicago Union Station to Aurora, Illinois. In 2010, the BNSF Line continued to have the highest weekday ridership of the 11 Metra lines. While Metra does not refer to its lines by particular colors, the BNSF line's color on Metra timetables is "Cascade Green," in honor of the Burlington Northern Railroad.

Metra is the primary commuter rail system in the Chicago metropolitan area serving the city of Chicago and its surrounding suburbs via the Union Pacific Railroad, BNSF Railway, and other railroads. The system operates 242 stations on 11 rail lines. It is the fourth busiest commuter rail system in the United States by ridership and the largest and busiest commuter rail system outside the New York City metropolitan area. In 2023, the system had a ridership of 31,894,900, or about 152,400 per weekday as of the fourth quarter of 2023. The estimated busiest day for Metra ridership occurred on November 4, 2016—the day of the Chicago Cubs 2016 World Series victory rally.