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 through the Chicago Subdivision. In 2010, the BNSF Line continued to have the highest weekday ridership (average 64,600) 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.

As of April 29, 2024, the public timetable shows 91 trains (44 inbound, 47 outbound) on the BNSF Line on weekdays. Of these, 32 inbound trains originate from Aurora, one from Downers Grove Main Street, nine from Fairview Avenue, and two from Brookfield. Five outbound trains terminate at Brookfield, eight at Fairview Avenue, three at Naperville, and the rest at Aurora. Weekend and holiday service consists of 36 trains (18 in each direction), with trains making all stops from Union Station to Aurora, save for a morning and afternoon inbound express train and an afternoon outbound train that run express from Union Station to Downers Grove Main Street.

Bike cars are available on weekday trains #1212 (leaves 5:29 A.M.,) #1252 (leaves 9:04 A.M.,) and #1284 (leaves 5:04 P.M.) inbound from Aurora, and trains #1217 (leaves 7:33 A.M.,) #1239 (leaves 3:10 P.M.,) and #1283 (leaves 6:50 P.M.) outbound to Aurora.

Bike cars are available on weekend trains #2002 (leaves 6:20 A.M.) and #2012 (leaves 10:20 A.M.) inbound from Aurora, and trains #2003 (leaves 8:40 A.M.) and #2013 (leaves 2:40 P.M.) outbound to Aurora.

The line is operated by BNSF under a "purchase of service agreement" with Metra, inherited from Burlington Northern. While Metra owns all rolling stock, the management and crews are BNSF employees. BNSF is the owner of the right-of-way, controls the line and handles dispatching from corporate headquarters in Fort Worth, Texas. Metra imposes a 70 mph maximum allowed speed for passenger trains. The BNSF Line may be the only Metra commuter line that operates via purchase-of-service agreements as of 2024 due to the Union Pacific Railroad announcing its intentions to transfer the operations and supplying of commuter trains to the Metra system itself for the routes originating from the Ogilvie Transportation Center.

The railroad between Chicago and Aurora was constructed in 1864 by the Chicago and Aurora Railroad, which evolved into the Chicago, Burlington and Quincy Railroad. The CB&Q operated the commuter service until the railroad merged into the Burlington Northern Railroad in 1970. Burlington Northern merged with the Atchison, Topeka and Santa Fe Railway in 1995 to form the Burlington Northern Santa Fe Railway, which would later rename itself to BNSF Railway.

When the Regional Transportation Authority (RTA) began subsidizing Chicago's commuter rail operations in 1974, Burlington Northern continued to operate its line under contract to the RTA. This arrangement continued when the RTA organized its commuter rail lines under the RTA Commuter Rail Division in 1983, later rebranded as Metra in 1985.

Today, the triple-track line is one of the busiest rail corridors in the United States. In addition to the 91 Metra trains that currently use the line, BNSF freight trains frequent the line at all hours. Amtrak's Southwest Chief, California Zephyr, and Illinois Zephyr and Carl Sandburg use the line as well, making an intermediate stop at Naperville. The Illinois Zephyr and Carl Sandburg services also stop at La Grange Road. Rail fans have coined the line as the "BNSF Racetrack".

The Clyde station at South Austin Boulevard and West 29th Street in Cicero was closed on April 1, 2007 due to low ridership and its dilapidation. In the months before its closure, it was used by about 50 passengers a day.

There have been proposals to extend service west into Kendall County, which as of 2020 is outside the RTA's service area. Potential new stations would be built in Montgomery, Oswego, Yorkville, Plano, and Sandwich, Illinois. The Plano station would be located over 1 mile west of the CB&Q Depot currently used by Amtrak's Illinois Zephyr and Carl Sandburg trains.

Between 2014 and 2019, annual ridership declined 7% from 16.7 million to 15.5 million passengers. Due to the COVID-19 pandemic, ridership dropped to 3,659,617 passengers in 2020.

The BNSF Line's locomotive fleet consists of the EMD F40PH-3 and the EMD F40PHM-3. Until 2012, some MPI MP36PH-3S locomotives (401-405) also operated on the line; however, they were reassigned to the Milwaukee lines and the North Central Service due to operating difficulties. Passenger cars include Gallery Cars from Pullman (Bike Car), Budd, Morrison-Knudsen/Amerail, and Nippon Sharyo.

County	Zone	Location	Station	Connections and notes
Cook	1	Chicago	Union Station	Amtrak (long-distance): California Zephyr, Capitol Limited, Cardinal, City of New Orleans, Empire Builder, Lake Shore Limited, Southwest Chief, Texas Eagle Amtrak (intercity): Blue Water, Borealis, Hiawatha, Illini and Saluki, Illinois Zephyr and Carl Sandburg, Lincoln Service, Pere Marquette, Wolverine Metra: ■ Milwaukee District North, ■ Milwaukee District West, ■ North Central Service, ■ Heritage Corridor, ■ SouthWest Service Chicago "L": Blue (at Clinton), Brown Orange Pink Purple (at Quincy) CTA Bus: 1, 7, J14, 19, 28, 56, 60, 120, 121, 124, 125, 126, 128, 130, 151, 156, 157, 192 Pace Bus: 755 Amtrak Thruway: Chicago–Madison and Chicago–Rockford (Van Galder), Chicago–Louisville (Greyhound)
	2		Halsted Street	CTA Bus: 8, 18, N62
			Western Avenue	Chicago "L": Pink (at Western) CTA Bus: 18, 49, X49
		Cicero	Cicero	CTA Bus: 35, 54, 54B, 60
			Morton Park	Closed between 1938 and 1957
			Clyde	Closed April 1, 2007
		Berwyn	La Vergne (rush only)	Pace Bus: 302, 314
			Berwyn	Pace Bus: 302, 311
			Harlem Avenue	Pace Bus: 302, 307
		Riverside	Riverside
		Brookfield	Hollywood
			Brookfield	Pace Bus: 331
	3		Congress Park (rush only)	Pace Bus: 302, 331
		La Grange	La Grange Road	Amtrak: Illinois Zephyr and Carl Sandburg Pace Bus: 302, 330, 331
			Stone Avenue (rush only)
		Western Springs	Western Springs
DuPage		Hinsdale	Highlands (rush only)
			Hinsdale
			West Hinsdale (rush only)
		Clarendon Hills	Clarendon Hills
		Westmont	Westmont	Pace Bus: 715
		Downers Grove	Fairview Avenue
	4		Downers Grove Main Street	Pace Bus: 834
			Belmont	Grove Commuter Shuttle: West Route
		Lisle	Lisle
		Naperville	Naperville	Amtrak: California Zephyr, Illinois Zephyr and Carl Sandburg, Southwest Chief Pace Bus: 530, 714, 722 Burlington Trailways: Chicago–Davenport
		Naperville/ Aurora	Route 59	Pace Bus: 559 Greyhound Lines: Chicago–Davenport
		Eola	Eola	Closed to passengers prior to 1971, closed entirely later
Kane		Aurora
			Scraper Works	Closed 1974
			Aurora	Pace Bus: 524, 530, 533, 540, 802
			Aurora (CB&Q Depot)	Closed 1986

• Metra BNSF Railway Service Schedule
• Thornapple River Rail Series BNSF's Metra Racetrack: A Railroad Superhighway