San Sebastiano in Vallepiatta is an ancient church next to Piazzeta della Selva in Siena, Italy.

On the main altar there is a Spoliation of Christ by Luigi Ademollo, and a 15th-century Crucifix, which legend holds was donated to the Compagnia di San Giovanni Battista della Morte (Company of St John the Baptist of the Death) by St Bernard himself.

The interior was frescoed in the 16th century by Giovanni Paolo Pisani, Raffaello Vanni, and Astolfo Petrazzi.

The main altarpiece is a bas-relief in stucco and terracotta depicting the venerated Madonna della Selva, and is attributed to Francesco di Giorgio Martini.

This article about a church building or other Christian place of worship in Italy is a stub.