Concatedral de San Nicolás el Magno, Neoclassical Catholic co-cathedral in Rionegro, Colombia.

The Concatedral de San Nicolás el Magno is a neoclassical church on the eastern side of Rionegro's main square, with a rectangular plan divided into three naves separated by lime-and-brick arches. Its walls rise in lime and brick to about a vara and a half, then continue in rammed earth. The 1926 facade by Tomás Uribe U. and Agustín Goovaerts, finished in 1940, gives the building its present appearance.

A first chapel dedicated to Saint Nicholas was built between 1662 and 1668 on land donated by Magdalena Gómez. On 8 March 1793 Bishop Ángel Velarde y Bustamante ordered its demolition, and the new church, modeled on Medellín's Candelaria, was inaugurated on 8 September 1804. In 1926 Tomás Uribe and Agustín Goovaerts redesigned the facade in neoclassical style, completed in 1940.

The church is a Marian sanctuary venerating Nuestra Señora Santa María de la Purísima Concepción del Santísimo Rosario de Arma, patroness of Rionegro and the diocese; her coronation took place on 8 February 1959, presided over by Archbishop Paolo Bertoli. The former sacristy, where the 1812 constitution was signed, now holds the Museo de Arte Religioso, with Quito-school paintings and sculpture, religious silverwork, vestments, books and furniture.

Visitors can stop by throughout the week and weekends to explore the architecture and religious art collection. It is advisable to wear respectful clothing and remain quiet during Mass times.

In 1812, the Constitution of the Independent State of Antioquia was signed within these walls, marking a pivotal moment in Colombian independence. This event made the building a symbol of political transformation during the independence movement.