Louis-Zéphirin Joncas (26 July 1846 – 28 March 1903) was a Canadian civil servant, journalist and politician. Born in Grande-Rivière, Lower Canada, the son of Léon Joncas and Esther Beaudin, Joncas was educated at the Collège Masson in Terrebonne and studied law in Montreal. He came back to Grande-Rivière to help his family financially and was a teacher. He later worked as an accountant, general agent, and manager of the Gaspé Fishing Company in Grande-Rivière.