Palazzo Sansedoni, Siena, Gothic palace in Piazza del Campo, Siena, Italy.

Palazzo Sansedoni is a Gothic urban palace whose concave brick facade follows the curve of Piazza del Campo, opposite the Palazzo Pubblico. It was formed after the mid-13th century by merging nearly five private houses and closing one access point to the square. Three orders of trifore windows cross the facade, and the tower, once rhombus-shaped in plan, was lowered in 1760.

Construction of this palace began in the mid-13th century by merging five separate residences into one large structure. Master masons completed the project in the early 14th century.

The private chapel ceiling holds Anton Domenico Gabbiani's Glory of the Blessed Ambrogio Sansedoni, painted in 1701. Other rooms carry 18th-century decoration by Francesco and Giuseppe Melani and Gian Domenico Ferretti. The name Sansedoni refers to the Sienese family that commissioned the Gothic refacing of the palace.

This palace is currently used by the Fondazione Monte dei Paschi di Siena for offices and exhibition spaces, so access may be limited. Visitors should check beforehand whether tours or exhibition access are available.

The tower once had an irregular rhombus-shaped plan; it was lowered in 1760, and some sources say it was truncated so as not to exceed the height of the Torre del Mangia. The ground floor once housed shops lining the street and the campo.