The Union Pacific West Line (UP-W) is a Metra commuter rail line operated by Union Pacific Railroad in Chicago, Illinois and its western suburbs. Metra does not refer to its lines by particular colors, but the timetable accents for the Union Pacific West line are "Kate Shelley Rose" pink, honoring an Iowa woman who saved a Chicago & North Western Railway train from disaster in 1881. Green and yellow were already selected for the Union Pacific North Line and Union Pacific Northwest Line, respectively, so pink was chosen for this line. Therefore, the UP-W is the only Metra line that uses a color to honor a person instead of a fallen flag railroad. Until the late 1940s the line had a branch to Freeport, Illinois. It diverged from the main line at West Chicago and had stations at Elgin, Marengo, Belvidere, Rockford, Freeport, and other communities. The line was once known as the Chicago & Northwestern/West Line until UP took over the C&NW in 1995. All Metra trains on this line terminated at Geneva until 2006, when the line was extended to its present terminus in Elburn. The line runs as part of the Union Pacific Railroad's Geneva Subdivision.

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.