The 2S4 Tyulpan (often spelled Tulpan, ; ) is a Soviet self-propelled mortar. "2S4" is its GRAU designation. It was identified for the first time in 1975 in the Soviet army and so was called M-1975 by NATO (the 2S7 Pion also received the M-1975 designation), whereas its official designation is SM-240(2S4). Its design is based on the GMZ tracked minelaying vehicle carrying an externally mounted M-240 240 mm breech-loading mortar on the rear of the hull. The Tyulpan is currently the heaviest mortar in deployment among any country.