The Basilica of San Francesco is a church in Siena, Tuscany, Italy. It was erected in c. 1228-1255 and later enlarged in the 14th-15th centuries, the original Romanesque edifice being turned into the current large Gothic one.

The basilica is on the Egyptian Cross plan, with a nave covered by spans and a transept, according to type favoured by the Mendicant Orders, which needed spaces capable to house large crowds of faithful.

The current interior looks rather sober after a fire in 1655 and the restoration of 1885-1892, when much of the Baroque altars were demolished (part of the paintings has been however returned in recent times). The hut-shaped, neo-Gothic façade, flanked by the 1763 campanile, dates to the early 20th century. The medieval marble decoration and the 15th century portal were removed in that occasion.