The first astronaut was either the Soviet Yuri Gagarin or the Soviet dog Laika, depending on whether you restrict your definition of astronaut based on species. We'll look at the accomplishments of both in this article.

Laika, a name that literally means "barker" and was based on her breed, was launched into space on 3 November 1957 on board Sputnik 2, becoming the first animal to orbit the Earth. This is only a month after the first satellite, Sputnik, was launched on 4 October 1957. Sputnik 2 is the second spacecraft launched into Earth orbit. Laika was selected from the pound, and at one time was a homeless dog wandering the streets of Moscow. She died only a few hours after launch, due to stress and overheating from a malfunctioning thermal control unit. As the technology to return a payload to Earth was not available at the time, it was planned to put the canine astronaut to sleep with poisoned food on the 10th day of flight.

The cabin of Sputnik 2 included a life-support system with an O2 generator, a fan that was supposed to activate when the temperature exceeded 15 degrees Celsius (59 degrees F), gelatinous food for a 10-day flight, and a bag to collect waste. But when some of the thermal insulation tore loose after separation of the last stage, the temperature of the cabin increased to 104 degrees F, and Laika died within 5 to 7 hours after great stress. The precise cause of Laika's death was not made public until decades later. Still, Laika is often acknowledged as the first true astronaut.

As satellite and space technology rapidly progressed, the Soviet Union once again decided to pioneer the way forward in space by launching the first human astronaut, Yuri Gagarin, on 12 April 1961, about three and a half years after the launch of Sputnik. Launched on board Vostok 1, Gagarin orbited the Earth just once, which took 108 minutes, then ejected from the capsule about 7 km above the ground, parachuting to Earth only a few hundred miles away from the launch size in Kazakhstan. Some villagers witnessed Vostok 1 impact the ground near where Gagarin landed with his parachute. Being the world's first astronaut, Gagarin instantly became an international celebrity.