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.

However, his studies were interrupted by the war and he instead enlisted in the British Army, serving in France with the 2nd Dragoon Guards.

After the retirement of Harold Luxton, he defeated J. J. Liston by a single vote in the lord-mayoral election.

He originated the idea of the MacRobertson Air Race to draw international attention to the city, and convinced Macpherson Robertson to sponsor it.

At the 1940 state election, he was the unsuccessful candidate in the electorate of Mornington, representing the United Australia Party.