The IND Queens Boulevard Line, sometimes abbreviated as QBL, is a line of the B Division of the New York City Subway in Manhattan and Queens, New York City. The line, which is underground throughout its entire route, contains 23 stations. The core section between 50th Street in Hell's Kitchen, Manhattan, and 169th Street in Jamaica, Queens, was built by the Independent Subway System (IND) in stages between 1933 and 1940, with the Jamaica–179th Street terminus opening in 1950. As of 2015, it is among the system's busiest lines, with a weekday ridership of over 460,000 people.
The Queens Boulevard Line's eastern terminus is the four-track 179th Street station. The line continues westward then northwest as a four-track line with the local tracks to the outside of the express tracks. The Queens Boulevard Line merges with the IND Archer Avenue Line east of Briarwood and with Jamaica Yard spurs west of Briarwood and east of Forest Hills–71st Avenue. The express tracks and the local tracks diverge at 65th Street in Jackson Heights and merge again at 36th Street in Sunnyside. West of 36th Street, the IND 63rd Street Line splits off both pairs of tracks, entering Manhattan via the 63rd Street Tunnel. At Queens Plaza in Long Island City, the line narrows to two tracks, with the local tracks splitting into the 60th Street Tunnel Connection and the IND Crosstown Line. From there, the express tracks of the line provide crosstown service across Manhattan under 53rd Street before turning southwest at Eighth Avenue, ending at the 50th Street station. The two-track section west of Queens Plaza is also known as the IND 53rd Street Line.