The 121st Street station is a skip-stop station on the elevated BMT Jamaica Line of the New York City Subway. Located at the intersection of 121st Street and Jamaica Avenue in Richmond Hill and Kew Gardens, Queens, it is served by the Z train during rush hours in the peak direction and the J train at all other times.

The BMT Jamaica Line, also known as the Broadway - Brooklyn Line, is an elevated rapid transit line of the B Division of the New York City Subway, in Brooklyn and Queens, New York City, United States. It runs from the Williamsburg Bridge southeast over Broadway to East New York, Brooklyn, and then east over Fulton Street and Jamaica Avenue to Jamaica, Queens. In western Jamaica, the line goes into a tunnel, becoming the lower level of the Archer Avenue lines in central Jamaica. The J and Z trains serve the entire length of the Jamaica Line, and the M serves the line west of Myrtle Avenue.