The IS-1 was the first in the Iosif Stalin series of heavy tanks that were named after the Soviet premier. They were designed to succeed the KV series, which by 1943 began showing their age particularly when pitted against the Panther. The IS-1 was based on a slightly modified hull of the KV-85 but proved to have superior mobility and armor protection. More importantly, it was based around a more powerful 85mm gun which was seen as necessary to combat the new generation of German tanks. In order to fit the larger gun, the turret had to be increased in order to maintain some degree of crew comfort. As was the case with subsequent IS tanks, the design was kept compact in order to maintain a lower weight that would be the case for heavy tanks; in fact, the IS-1 weight roughly the same as the much earlier KV-1 with a lighter gun. Profile was kept low, and like some other Soviet tanks, external fuel tanks were often mounted on the rear hull sides. Combat experience of the IS-1 was mixed, with criticism focused primarily on the gun which was urged to be upgraded. This resulted in the successful IS-2 with a 122mm gun that soon replaced the IS-1 in production after only a small number had been built.

The first Iosif Stalin tank began life as the K-13 prototype which was first tested in May 1942. This subsequently resulted in the IS-85 (Ob'yekt 233) prototype which was then redesignated as the IS-1 when in production. Given the small production run, there were no variants.