James 'Jimmie' Wallace Stewart (1921 – 10 June 2006), was a professor of haematology at Middlesex Hospital, London.
Stewart was born in Assam, India, where his father was a medical doctor.
At the age of ten, Stewart went to school at St George's College, Weybridge.
He was treasurer of the British Society for Haematology for its first 15 years, and a founder fellow of the Royal College of Pathologists.
His laboratory was one of the first in the United Kingdom to have a Coulter counter, and he helped to develop quality assurance in haematology.