Richard Adolf Zsigmondy (Vienna, April 1, 1865 – Göttingen, September 23, 1929 ) was an Austrian chemist. Together with Heinrich Siedentopf he invented in 1903 the ultramicroscope, which they developed for the analysis of submicroscopic particles. Zsigmondy was professor and director of the institute of inorganic chemistry at the University of Göttingen from 1907 until 1929. For his researches in colloidal chemistry and for developing in this connection the ultramicroscope, he received the 1925 Nobel Prize in chemistry. Apart from Lehrbuch der Kolloidchemie [Textbook of colloid chemistry], Zsigmondy wrote Über das kolloide Gold [About colloidal gold] in collaboration with P.A. Thiessen and Colloids and the ultramicroscope: A manual of colloid chemistry and ultramicroscopy (1905, translated into English 1909).