The SU-100Y was a Soviet prototype developed from the chassis of the T-100 heavy tank prototype in the Winter War. The vehicle was intended to fill a similar purpose as that of the KV-2, using its 130mm naval gun to provide support to infantry against fortified positions. The use of a high velocity 152mm gun was also proposed. The tank never made it past a prototype phase, although the single prototype built was reportedly used in the defence of Moscow in 1941. The sole model in existence is currently preserved at the Kubinka Tank Museum.

It was introduced in Update 1.51 "Cold Steel". The SU-100Y is a very heavy tank destroyer with an extremely powerful gun. The tank features mediocre armour at the front, and can be penetrated with ease by most enemies around its BR at close ranges. Its mobility can be considered average at best, reaching it's top speed relatively quickly for a tank of it's size, although the reverse speed is very poor. Its gun is a 130mm B-13 naval gun which uses SAPCBC as its regular ammo. Boasting a large amount of explosive filler and high penetration even at long ranges, the SU-100Y has no trouble destroying enemy tanks.