Russia celebrates Cosmonautics Day on April 12 in honor of Gagarin's incredible 1961 feat, and in celebration of the thousands of Soviet scientists and engineers who made his flight possible. In 2011, the United Nations General Assembly declared April 12 to be the International Day of Human Space Flight.
To find out more about Gagarin's epic journey from Air Force pilot to the world's first space traveler, check out Sputnik's video.