Guy Frederic Marrian (3 March 1904 – 24 July 1981) was a British biochemist mainly known for his research into oestregen.

He was born in London on 3 March 1904 the son of Mary Eddington Currie and Frederic York Marrian, a civil engineer.

He then went to work as a laboratory assistant to Dr Henry Dale at the National Institute of Medical Research in Hampstead.

In 1933 he obtained a position as Assistant Professor of Biochemistry at the University of Toronto in Canada.

During the war he was seconded to the Chemical Warfare Field Station in Alberta at the rank of Major.