Sputnik 2, or Prosteyshiy Sputnik 2, launched on 3 November 1957, was the second spacecraft launched into Earth orbit, and the first to carry an animal into orbit, a Soviet space dog named Laika.

During the 1950s and 1960s the Soviet space program used dogs for sub-orbital and orbital space flights to determine whether human spaceflight was feasible. These dogs, including Laika, the first animal to orbit Earth, were surgically modified to provide the necessary information for human survival in space. The Soviet space program typically used female dogs due to their anatomical compatibility with the spacesuit. Similarly, they used mix-breed dogs due to their apparent hardiness.