Saint Catherine of Siena's Monastery, Buenos Aires, Dominican monastery in Retiro, Buenos Aires, Argentina.

Saint Catherine of Siena's Monastery is a Dominican religious complex in Retiro spanning an entire city block with two central courtyards and cells designed for approximately forty Dominican nuns. The buildings feature colonial-era architecture arranged around these internal open spaces.

Dionisio de Torres Briceño obtained royal authorization in 1717 to found a Dominican convent; work on plans by Jesuit Juan Bautista Prímoli and Andrés Bianchi began in 1727 at Defensa and México, then halted after Briceño's death in 1729. Juan de Narbona won the 1737 tender, moved the site to the Manzana del Campanero and started building in 1738. Five nuns arrived from Córdoba on 25 May 1745, and the church was inaugurated on 21 December 1745.

The monastery was founded in 1745 by five nuns from the Santa Catalina de Siena convent in Córdoba, joined by five postulants who had arrived since May. They were taken by carriage to the cathedral and walked in procession to the new house, accompanied by the bishop and both cabildos; the city stayed lit for three nights.

The monastery occupies the block bounded by San Martín, Viamonte, Reconquista and Avenida Córdoba. The main church door on San Martín was closed in 1875 and the entrance moved to Viamonte, next to the sacristy. The church has a single nave; a grilled opening left of the presbytery connects to the lower choir, and galleries with round windows above the narthex let the nuns follow services unseen.

During the British invasion of 1807, the monastery transformed into a hospital treating wounded soldiers from both opposing sides. This unexpected role reveals how religious buildings were pressed into service during military conflict.