The mission of the Soviet spacecraft Sputnik 25 was an attempted lunar soft landing, with the purpose of returning data on the mechanical characteristics of the lunar surface, the hazards presented by the topology such as craters, rocks, and other obstructions, and radiation, in preparation for future manned landings. The 1500 kg spacecraft consisted of a cylindrical section containing maneuvering and landing rockets and fuel, orientation devices and radio transmitters and a spherical top containing the 100 kg lander. The lander would be ejected onto the surface after the main body touched down, carrying a camera and devices to measure radiation.

The spacecraft was injected into Earth orbit successfully by the SL-6/A-2-e launcher but failed to escape orbit for its trip to the Moon. Its orbit decayed on January 5, 1963 after one day.

In the U.S. Naval Space Command Satellite Situation Summary Sputnik 25 was originally designated Sputnik 33, and the name Sputnik 25 was used for Sputnik 21.