Louis-Léon Lesieur Désaulniers (February 20, 1823 – October 31, 1896) was a Quebec physician and political figure.

He represented Saint-Maurice in the House of Commons of Canada as a Conservative member from 1867 to 1868 and from 1879 to 1887.

He was elected to represent Saint-Maurice in the Legislative Assembly of Canada in 1854, 1858 and 1861 as a member of the parti bleu, then was defeated in 1863.

He was elected to the 1st Canadian Parliament in 1867 but resigned in 1868 to become inspector for prisons and asylums in Quebec, later serving as president of that agency.

His son Eugène Merrill was later a member of the Legislative Assembly of Quebec.