Sé de Portalegre, Cathedral and National Monument in Portalegre, Portugal.

The Sé de Portalegre is a Mannerist cathedral begun in 1556 to a design by Afonso Álvares, with a facade mixing 16th- to 18th-century elements and 28 windows. Its interior has three naves with barrel vaults and round arches; the main altar retable has eight panels, with the chapels of the Santíssimo and São Pedro flanking it, and marble pulpits and railings.

Bishop Julião de Alva founded the cathedral for the new Diocese of Portalegre; work began on 14 May 1556 on the site of the Igreja de Santa Maria do Castelo, with expropriations authorised by João III from 1553. The design is by Afonso Álvares, and the keystone of the vault was set in 1575. Bishop Manuel Tavares restored it in 1795, giving it its present appearance.

The cathedral is also the parish church of Nossa Senhora da Assunção. Queen Maria II gave it a bell cast in Estremoz, and the north side faces the cloister. Twelve side chapels hold retables restored between 2021 and 2023, when wall paintings from the late 16th to 18th centuries were found in them.

The cathedral reopened on 16 March 2023 after rehabilitation works begun in February 2021, which also covered the cloisters and the restoration of the retables in the twelve interior chapels and the Chapel of São Tiago. The north side facade faces the street, while the south side looks onto the cloister. The two towers each have four round-arched openings holding the bells.

During the 2021–2023 restoration, mural paintings from the late 16th, 17th and 18th centuries were found in the chapels of the cathedral, hidden until then. The same works restored the retables of the 12 interior chapels and of the Chapel of São Tiago.