Prof Alexander Boyd Stewart CBE FRSE FRIC (1904–1981) was a 20th century Scottish organic chemist and agriculturalist.
He was born on 3 November 1904 at Tarland in Aberdeenshire, the son of Donald Stewart, a farmer.
He immediately obtained a post as Head of the Soil Fertility Department at the Macaulay Institute.
His proposers were Donald McArthur, David Cuthbertson, A. T. Phillipson, Thomas Phemister, James Robert Matthews and Murray Macgregor.
He retired in 1968 and died at his home, 3 Woodburn Place (a 1980s bungalow) in Aberdeen on 27 February 1981.