The (Co-)Cathedral of Castelo Branco or Church of Saint Michael (archangel) (Portuguese: Sé de Castelo Branco, Igreja de São Miguel) is a Roman Catholic Latin Co-cathedral and former cathedral in Castelo Branco, Portugal.
It is the second official seat of the Catholic Diocese of Portalegre-Castelo Branco, as the bishopric's two-part title suggests, ranking after the Cathedral of Portalegre.