The SU-85 (Samokhodnaya ustanovka 85) was a Soviet self-propelled gun used during World War II, based on the chassis of the T-34 medium tank.

As with the other AFVs in the SU series, the designation "85" refers to the vehicle's main armament, the 85 mm D-5T gun.

Although the Panther was not seen in combat until July 1943, the new generation of German vehicles meant the Red Army would need a new, more powerful main gun for their armoured formations.

Military planners directed the design bureaus of both Gen. Vasiliy Grabin and Gen. Fyodor Petrov to modify the 85 mm anti-aircraft gun for use as an anti-tank weapon.

The D-5T was capable of penetrating the Tiger I from 1000 m.[3] The vehicle had a low profile and excellent mobility.

Initially given an armored commander's cap on the first batch, the SU-85's observational optics were improved by the introduction of a standard commander's cupola - the same as on the T-34/76 model 1942 - in addition to the already existing prismatic observation sights installed in left side and rear.