Aimo Kaarlo Cajander (4 April 1879 in Uusikaupunki – 21 January 1943 in Helsinki) was, outside of botany, best known as Prime Minister of Finland up to the Winter War.He was a professor of Forestry 1911–34; director-general for Finland's Forest and Park Service 1934–1943; prime minister in 1922, 1924, and 1937–1939; chairman of the National Progressive Party 1933–1943; and Member of Parliament.