Césaire Thérien (January 12, 1824 – February 9, 1890) was a merchant and political figure in Quebec.
He was born in L'Assomption, Lower Canada, the son of Jean-Baptiste Thérien and Apolline Gariépy.
He worked as a clerk in his father-in-law Paul Colette's store before establishing himself as a merchant in Saint-Isidore.
After the death of his first wife, he married Ézilda Mazurette, dit Lapierre.
His widow married Louis Duhamel, who also served in the Quebec assembly.