Swedish botanist (1895–1967).
Gustaf Einar Du Rietz (25 April 1895 – 7 March 1967) was a Swedish botanist and lichenologist. His research interests included plant ecology, lichen taxonomy, and biogeography. He was a leading figure in the Uppsala school of phytosociology–the study of groups of species of plants that are usually found together–and is recognised for his role in advancing this field of science and for mentoring future lichenologists. He led the Swedish Australasian Botanical Expedition of 1926–27, a seven-month research tour of various locations. He was married to Greta Sernander, who was also a lichenologist.