Sir Harold Gengoult Smith (25 July 1890 – 14 April 1983) was an Australian medical practitioner who served as Lord Mayor of Melbourne from 1931 to 1934. Smith was born in Melbourne to Marion Jane (née Higgins) and Louis Lawrence Smith, both English immigrants. His father was a doctor and member of parliament, while his sister was the musical publisher Louise Hanson-Dyer. Smith attended Melbourne Grammar School and then moved to Scotland to study medicine. However, his studies were interrupted by the war and he instead enlisted in the British Army, serving in France with the 2nd Dragoon Guards. Smith eventually received his qualifications in medicine in 1917. He subsequently returned to Australia and began practising at his father's chambers on Collins Street.