Sir Alfred William Flux CB (8 April 1867 – 16 July 1942) was a British economist and statistician.

Flux was born in the Landport district of Portsmouth in 1867, the son of a cement maker.^[1] He attended Portsmouth Grammar School then studied mathematics at St John's College, Cambridge, where he was a Senior Wrangler in 1887^[2] (sharing the honour in a tie with three others). While at Cambridge he became friends with Alfred Marshall, who interested him in economics. He was a foundation member of the Economic Society (1890). In 1893 he was appointed as Cobden Lecturer in Political Economy at Owens College, Manchester^[3] and from then until 1908 taught economics, at Manchester and then at McGill University, Montreal.^[4] In 1897, while in Manchester he married Harriet Emily Hansen, a Danish woman.^[1] He served as secretary of the Manchester Literary and Philosophical Society in 1900–1901.

Flux returned to London in 1908 to take up a post as advisor to the Commercial, Labour and Statistics Department. In 1918, he was appointed Head of the Statistics Department of the Board of Trade.^[1] The Royal Statistical Society awarded him the Guy Medal in Silver in 1921 and in Gold in 1930. He also served as President of the Society between 1928 and 1930.^[5]

Flux retired to Denmark in 1932 and was knighted in 1934. He died of pneumonia in 1942, aged 75.^[1][2]