Joseph-Octave Plessis (March 3, 1763 – December 4, 1825) was a Canadian Roman Catholic clergyman from Quebec. He was the first archbishop of the Roman Catholic Archdiocese of Quebec after the diocese was elevated to the status of an archdiocese. Plessis cultivated a new generation of priests during the difficult period leading up to the Lower Canada Rebellion, including Jean-Baptiste-Antoine Ferland, Narcisse-Charles Fortier, Jean-Baptiste Kelly, Thomas Maguire, and Pierre-Antoine Tabeau.