Marie Joseph Demers (May 31, 1871 – July 28, 1940) was a Canadian politician.

Born in St-Georges d'Henryville, Quebec, the son of Alexis-Louis Demers, former M.L.A.

for Iberville, and the brother of Louis Philippe Demers, who sat in the House of Commons of Canada from 1900 to 1906 until he was appointed a Puisne Judge, Superior Court.

He was elected to the House of Commons for St. Johns—Iberville in the by-election called after his brother was appointed a judge.

He resigned in 1922, when he accepted of an office of emolument under the Crown.