Soviet cosmonaut, who piloted the Vostok 3 spacecraft, launched August 11, 1962. When Vostok 4, piloted by Pavel R. Popovich (Popovich, Pavel Romanovich), was launched a day later, there were, for the first time, two manned craft in space simultaneously. The two made radio and visual contact, but there was no attempt at docking. Both landed on August 15.

The son of a worker on a collective farm, Nikolayev studied and worked in forestry until drafted into the Soviet army in 1950. An early interest in flying persisted, and he soon transferred to the air force; in 1954 he became a pilot. In 1957 he joined the Communist Party, and in March 1960 he entered cosmonaut training. In 1962 he became the third Russian cosmonaut to travel into space, and during his 96-hour flight, which set an endurance record, he orbited the Earth 64 times. Nikolayev later served as the commander of the Soviet Astronauts' Detachment.

On November 3, 1963, Nikolayev married Valentina Tereshkova (Tereshkova, Valentina), who in June 1963 had become the first woman to travel in space. They had one child and were subsequently divorced.

Nikolayev and Vitaly I. Sevastyanov manned the Soyuz 9 flight on June 1, 1970, and set a new space endurance record of almost 18 days in orbit. The mission, primarily one of determining the effects of prolonged spaceflight, ended on June 19. Nikolayev was twice named Hero of the Soviet Union.