Jean-Baptiste Mongenais (November 24, 1803 – May 28, 1887) was a Quebec businessman and political figure.
He was a Conservative member representing Vaudreuil in the House of Commons of Canada from 1879 to 1882.
He became a farmer and merchant and was also a shareholder and administrator for the Vaudreuil Railway Company.
Mongenais was a justice of the peace and served in the local militia, becoming lieutenant-colonel in 1869.
His son-in-law, Hugh McMillan, also represented Vaudreuil in the House of Commons.