The International Union of Geodesy and Geophysics (IUGG) was established in 1919 to promote activities of international scientific societies dealing with geodesy, terrestrial magnetism and electricity, meteorology, physical oceanography, seismology, volcanology, and hydrology. This paper first introduces IUGG, presenting its current structure, partners, and various activities before the origin and earlier development of the Union is described covering the period between the two World Wars.

This paper describes the history of the International Union of Geodesy and Geophysics (IUGG) after World War II. The technologies developed during the war were brought to bear in the extraordinary global scientific effort that was the International Geophysical Year (1957–1958). Changes in the geopolitical landscape brought about changes in IUGG's structure. International campaigns encompassing multiple disciplines became commonplace, and international scientific bodies were organized.

Written for the centennial anniversary of the International Union of Geodesy and Geophysics (IUGG), this paper documents the activities of the Union at the beginning of the 21st century. IUGG added an eighth association on cryospheric sciences, introduced new categories of affiliate and honorary memberships, new grants, science education, and recognition programs, and formed new commissions on climatic and environmental change, data and information, planetary sciences, and history.