Ragnar Sandegren (1887–1966) was a member of the Geological Society of Sweden since 1910, its Secretary 1926–1937 and 1952–1954. He was the editor of the GFF during the same periods and in 1955–1957 and was one of the holders of those two Plaquettes of Merit which the Society has awarded hitherto. This paper contains a biography of Sandegren as a peat geologist at the Geological Survey, a mapping state geologist, and the leading biographer in the field of Swedish geology. A bibliography of Sandegren's publications is added.