The International Geophysical Year (IGY) of 1957–1958 was one of the most significant scientific events of the 20th century that marked the beginning of the Space Age. IGY united efforts of scientists from 67 countries for comprehensive study of our planet. The scientific program included multidisciplinary activity on all the continents, in the oceans, in the air, and in space. This article gives a brief overview of the history of the IGY organization and its main achievements.