The International Union of Radio Science (URSI) is a major international union of scientists and nations devoted to scientific studies of radio science, including not only the transmission of information from transmitter to a distant receiver, but also the acquisition of information about our planet by means of radio techniques.

URSI scientific activities encompass research in radio theory and practice from ELF waves to optical waves. The union encourages and fosters cooperation among international scientists on matters pertaining to radio. The URSI comprises ten commissions, each devoted to an aspect of radio science.

The URSI was founded in 1919 during the Constitutional Assembly of the International Research Council, but it finds its origins in 1913 as the natural successor to the Commission Internationale de Telegraphie sans Fil.