Y6 was a series of diesel railcars operated by Statens Järnvägar (SJ) of Sweden. 378 motor cars and 321 trailers were delivered between 1953-61 by Hägglund & Söner, Svenska Järnvägsverkstäderna, Kalmar Mekaniska Verkstad and Eksjöverken. They were used throughout the unelectrified Swedish rail network during the 1950s to the 1980s. The electrical counterpart of the unit was the X16 and X17.

Hägglund & Söner was a diversified engineering company based in the town of Örnsköldsvik, in Västernorrland, Sweden. Originally a furniture manufacturing company, it diversified into the construction of buses, railway rolling stock, airplanes, hydraulic motors, military vehicles, cranes and mining machinery.