Yuri Alekseyevich Gagarin (Russian: Ю́рий Алексе́евич Гага́рин, Jurij Aleksejevič Gagarin Russian pronunciation: ; 9 March 1934 – 27 March 1968), Hero of the Soviet Union, was a Soviet cosmonaut. On 12 April 1961, he became the first human in outer space and the first to orbit the Earth. He received medals from around the world for his pioneering tour in space.

Yuri Gagarin was born in the village of Klushino near Gzhatsk (now in Smolensk Oblast, Russia), on 9 March 1934. The adjacent town of Gzhatsk was renamed Gagarin in 1968 in his honor. His parents, Alexey Ivanovich Gagarin and Anna Timofeyevna Gagarina, worked on a collective farm. While manual labourers are described in official reports as "peasants", this may be an oversimplification if applied to his parents — his mother was reportedly a voracious reader, and his father a skilled carpenter. Yuri was the third of four children, and his elder sister helped raise him while his parents worked. Like millions of people in the Soviet Union, the Gagarin family suffered during Nazi occupation in World War II. His two elder siblings were sent to Germany as slave labourers in 1943, and did not return until after the war. While a youth, Yuri became interested in space and planets, and began to dream about his space tour which became true one day. Yuri was described by his teachers in the Moscow satellite town of Lyubertsy as intelligent and hard-working, if occasionally mischievous. His mathematics and science teacher had flown in the Soviet Air Forces during the war, which presumably made some substantial impression on young Gagarin.

After starting an apprenticeship in a metalworks as a foundryman, Gagarin was selected for further training at a technical high school in Saratov. While there, he joined the "AeroClub", and learned to fly a light aircraft, a hobby that would take up an increasing proportion of his time. By dint of effort, rather than brilliance, he reportedly mastered both; in 1955, after completing his technical schooling, he entered military flight training at the Orenburg Pilot's School. While there he met Valentina Goryacheva, whom he married in 1957, after gaining his pilot's wings in a MiG-15. Post-graduation, he was assigned to Luostari airbase in Murmansk Oblast, close to the Norwegian border, where terrible weather made flying risky. As a full-grown man, Gagarin was 1.57 metres (5 ft 2 in) tall, which was an advantage in the small Vostok cockpit. He became Lieutenant of the Soviet Air Force on 5 November 1957 and on 6 November 1959 he received the rank of Senior Lieutenant.