The collegiate church of San Martino is the main place of Catholic worship in Sinalunga, in the province of Siena, in the territory of the diocese of Montepulciano-Chiusi-Pienza.
The collegiate church, built in 1588 and restored in 2010, is located in the historic center of Sinalunga, in Piazza Garibaldi.
The exterior of the collegiate church is characterized by the facade. This is gabled and is covered with light plaster, with four Tuscan red brick pilasters. The portal opens in the center, preceded by a staircase and surmounted by a circular rose window. The facade is crowned by a triangular tympanum in the center of which there is a rectangular window. Next to the church stands the bell tower, with an octagonal peephole.
The interior of the collegiate church has a Latin cross plan structure, with a single nave and transept covered with a barrel vault. The nave, illuminated by natural light exclusively through the two windows on the counter-façade, is flanked by eight chapels, four on each side, inside each of which there is an altar. To the left of the portal, inside a niche, is the baptismal font, with a carved wooden lid. The cross vault is covered with an octagonal lantern. The presbytery is bordered by a marble balustrade and houses the main altar in stucco, surmounted by a polychrome marble tabernacle. Behind the altar, there are the wooden stalls of the choir.
Inside you can admire the following works: -Madonna and Child between Saints Martin and Sebastian by Benvenire di Giovanni.
-Madonna with Child and Saints by Sodom.
- Marriage of the Madonna by Rutilio Manetti (1612).
-Santa Caterina da Siena presents Sant'Antonio da Padova with Child to the Madonna by Francesco Nasini (1650).
- Saints Catherine of Siena, Domenico, Martino, Francesco, Lucia and Caterina d'Alessandria by Giuseppe Nicola Nasini (1697).