Monticiano is a town and comune on the right bank of the Val di Merse, Province of Siena, Tuscany, central Italy.

First historical mentions of the "Castle of Monticiano" dates from 1171, when it was under the suzerainty of the bishop of Volterra.

A system of agriculture quickly grew up around Monticiano, the principal product cultivated being wheat.

In 1266, due to its citizens' participation to the Ghibelline defeat at Benevento, it was occupied by the Sienese troops, who destroyed the castle walls.

The night time battle between the partisans and the Germans between the 3rd and 4 June 1944 which took place in the town's central piazza is particularly remembered.