Sir François-Xavier Lemieux (April 9, 1851 – July 18, 1933), often referred to as F.X. Lemieux, was a Quebec lawyer, judge and political figure. He represented Lévis in the Legislative Assembly of Quebec from 1883 to 1892 and Bonaventure from 1894 to 1897. Lemieux was also Louis Riel's lawyer in 1885. He was born at Lévis in 1851 and studied at the college there, at Quebec City and the Université Laval. He articled in law, was called to the Quebec bar in 1872 and became a successful criminal lawyer. In 1874, he married Diane, the daughter of judge Marc-Aurèle Plamondon.