The SU-100Y was a Soviet prototype self-propelled gun, developed from the prototype T-100 tank. It was developed during the Winter War with Finland to include a 130 mm gun to destroy concrete defensive structures like bunkers and anti-tank obstacles along with the use as a tank destroyer. It did not see production, but the prototype was brought into use in the Second World War in defence of Moscow and possibly in other operations as it stayed in service until the end of the war.