| Station: | Kosmos 557 (DOS-3) |
| Insignia: | Salyut program insignia.svg |
| Insignia Caption: | Salyut programme insignia |
| Cospar Id: | 1973-026A[1] |
| Satcat: | 6498 |
| Crew: | 3 (intended) |
| Launch: | UTC |
| Launch Pad: | LC-81/23, Baikonur Cosmodrome, USSR |
| Inclination: | 51.6 degrees |
| Period: | 89.1 minutes |
| In Orbit: | 11 days (22 May 1973) |
| Occupied: | 0 days (22 May 1973) |
| Orbits: | ~175 (22 May 1973) |
| As Of: | 11 May 1973 (Unless noted otherwise) |
| Configuration Image: | Salyut 4 and Soyuz drawing.svg |
| Configuration Caption: | The planned orbital configuration of DOS-3 |
Kosmos 557 (Russian: Космос 557 meaning Cosmos 557), originally designated DOS-3, was the third space station in the Salyut program. It was originally intended to be launched as Salyut-3, but due to its failure to achieve orbit on May 11, 1973, three days before the launch of Skylab, it was renamed Kosmos-557.
Due to errors in the flight control system while out of the range of ground control, the station fired its attitude thruster until it consumed all of its attitude control fuel and became uncontrollable before raising its orbit to the desired altitude. Since the spacecraft was already in orbit and had been registered by Western radar, the Soviets disguised the launch as "Kosmos 557" and quietly allowed it to reenter Earth's atmosphere and burn up a week later. It was revealed to have been a Salyut station only much later.