| Soviet locomotive class ИС | |
| Powertype: | Steam |
| Builder: | October Revolution Locomotive Factory, Voroshilovgrad (Luhansk) |
| Builddate: | 1932–1942 |
| Totalproduction: | 649 |
| Whytetype: | 2-8-4 |
| Leadingdiameter: | 10502NaN2 |
| Driverdiameter: | 18502NaN2 |
| Trailingdiameter: | 10502NaN2 |
| Boilerpressure: | 15sigfig=3NaNsigfig=3 |
| Firearea: | 7.04m2 |
| Totalsurface: | 295.2m2 |
| Superheaterarea: | 148.4m2 |
| Cylindercount: | Two, outside |
| Cylindersize: | 670x |
| Maxspeed: | 1150NaN0 |
| Tractiveeffort: | 233.5-1NaN-1 |
| Fleetnumbers: | IS20-1 |
| Retiredate: | 1965–1987 |
| Scrapdate: | 1975–1996 |
The Soviet locomotive class IS (Russian: ИС; Ukrainian: Паровоз ІС|Parovoz IS) was a Soviet passenger steam locomotive type named after Joseph Stalin (Russian: Иосиф Сталин; Ukrainian: Йосип Сталін|Yosyp Stalin). The contract design was prepared in 1929 at V.V. Kuybyshev Locomotive Factory in Kolomna, Russian SFSR. The IS series locomotives were manufactured between 1932 and 1942. The last one was built in 1942 during the Great Patriotic War against Nazi Germany.
The locomotive used the same cylinders and boilers as the FD series locomotives. However the IS steam locomotive had a 2-8-4 wheel arrangement.
The first steam locomotive was released from the Kolomna factory on October 4, 1932. In April–December a steam locomotive was tested on the October, Southern, and Ekaterinenskaya railways.
In 1936, production began at October Revolution Locomotive Factory in Voroshilovgrad, Ukrainian SSR (Luhansk, Ukraine). In total, 649 IS steam locomotives were constructed. Later the series was renamed FDP (steam locomotive FD, passenger modification).
These locomotives were used until 1972.