Louis Beaufort Stewart (27 January 1861 – 15 March 1937) was a Canadian astronomer, civil engineer and academic. He served as the president of the Royal Astronomical Society of Canada from 1912 to 1913, and played a key role in preserving the Toronto Magnetic and Meteorological Observatory building at the University of Toronto. Stewart stepped down from his academic post after reaching the mandatory retirement age in 1932. He remained active in scientific research until his death in 1937.