Thomas Semmes Walmsley was an American attorney and politician who was the mayor of New Orleans from July 1929 to June 1936. He is also known for his rivalry with Louisiana Governor Huey Long.

The post of Mayor of the City of New Orleans has been held by the following individuals since New Orleans came under American administration following the Louisiana Purchase — the 1803 acquisition by the U.S. of 828,800 square miles (2,147,000 km2) of the French province La Louisiane. In all mayoral elections since 1930, New Orleans has used a two-round system with a preliminary round and a runoff if no candidate reached a majority in the first round. All mayors of New Orleans since 1872 have been Democrats.