Sputnik 2 (Russian pronunciation: [ˈsputnʲɪk], Russian: Спутник-2, Satellite 2), or Prosteyshiy Sputnik 2 (PS-2, Russian: Простейший Спутник 2, Simplest Satellite 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.

Launched by the Soviet Union via a modified R-7 intercontinental ballistic missile, Sputnik 2 was a 4-metre-high (13 ft) cone-shaped capsule with a base diameter of 2 metres (6.6 ft) that weighed around 500 kilograms (1,100 lb), though it was not designed to separate from the rocket core that brought it to orbit, bringing the total mass in orbit to 7.79 tonnes (17,200 lb). It contained several compartments for radio transmitters, a telemetry system, a programming unit, a regeneration and temperature-control system for the cabin, and scientific instruments. A separate sealed cabin contained the dog Laika.

Though Laika died shortly after reaching orbit, Sputnik 2 marked another huge success for the Soviet Union in The Space Race, lofting a huge payload for the time, sending an animal into orbit, and, for the first time, returning scientific data from above the Earth's atmosphere for an extended period. The satellite reentered Earth's atmosphere on 14 April 1958.

In 1955, engineer Mikhail Tikhonravov created a proposal for "Object D", a satellite massing 1,000 kg (2,200 lb) to 1,400 kg (3,100 lb), about a fourth of which would be devoted to scientific instruments. Upon learning that this spacecraft would outmass the announced American satellite by nearly 1,000 times, Soviet leader Nikita Khrushchev advocated for the proposal, which was approved by the government in Resolution #149-88 of 30 January 1956. Work began on the project in February with a launch date of latter 1957, in time for the International Geophysical Year. The design was finalized on 24 July.

By the end of 1956, it had become clear that neither the complicated Object D nor the 8A91 satellite launch vehicle version of the R-7 ICBM under development to launch it would be finished in time for a 1957 launch. Thus, in December 1956, OKB-1 head Sergei Korolev proposed the development of two simpler satellites: PS, Prosteishy Sputnik, or Primitive Satellite. The two PS satellites would be simple spheres massing 83.4 kg (184 lb) and equipped solely with a radio antenna. The project was approved by the government on 25 January 1957. The choice to launch these two instead of waiting for the more advanced Object D (which would eventually become Sputnik 3) to be finished was largely motivated by the desire to launch a satellite to orbit before the US. The first of these satellites, Sputnik 1 (PS-1), was successfully launched 4 October 1957, and became the world's first artificial satellite.

Immediately following the launch, Nikita Khrushchev asked Sergei Korolev to prepare a Sputnik 2 in time for the 40th anniversary of the Bolshevik revolution in early November, just three weeks later. Details of the conversation vary, but it appears likely that Korolev suggested the idea of flying a dog, while Khrushchev emphasised the importance of the date.

With only three weeks to prepare, OKB-1 had to scramble to assemble a new satellite. While PS-2 had been built, it was just a ball, identical to PS-1. Fortunately, the R-5A sounding rocket had recently been used to launch a series of suborbital missions carrying dogs as payloads. Korolev simply requisitioned a payload container used for these missions and had it installed in the upper stage of its R-7 launching rocket directly beneath the PS-2 sphere. Upon reaching orbit, the final stage or Blok A would detach from the satellite. No provision was made for the dog's recovery.

Sputnik 2 was a 4-metre-high (13 ft) cone-shaped capsule with a base diameter of 2 metres (6.6 ft) that weighed around 500 kilograms (1,100 lb), though it was not designed to separate from the rocket core that brought it to orbit, bringing the total mass in orbit to 7.79 tonnes (17,200 lb).