The town of Semproniano has origins dating to the Middle Ages and it is known for its closeness to the famous baths of Saturnia, above all. The Oasis of the WWF in the Bosco dei Rocconi, the Centro for the Rescue of Wild Animals of the Maremma and the Rocchette di Fazio can be visited in Semproniano.

The chief town is at 662 m of altitude and it was mentioned with the name of "Casale Simprunianum" before the year 1000.
In the X century, a well-fortified stronghold with quite bulky walls already existed on the layer of travertine that characterizes the hills. The Aldobrandeschi, the major feudatories in the Grosseto's area, were the rulers of the territory and their family split into two branches, the one of the Sovana and the one of the Santa Fiora, in the XIII century. The Santa Fiora was the branch that obtained the area of Semproniano.
The fortress of Semproniano was taken by the Republic of Siena by force of arms (XIV century) and it became one of the scenes of the clashes between the "City of the Palio" and the Orsini of Pitigliano, a Roman-born family who aimed to dominate the country of Grosseto and annexed Semproniano. During one of these battles, the Sienese militia destroyed the walls of the castle. This action, condemned by the maximum representatives of the Republic of Siena, earned the Orsini the open hostility of the town's inhabitants, who chased them away definitively.
In the XVI century, the town of Semproniano, that was damaged by the invasion of the Spanish militia in 1536, passed under the rule of the Tuscan Grand Duchy with all the Sienese territories. This town lost its autonomy under the government of the Medici, before, and under the Hapsburg-Lorraine, later. Semproniano recuperated its autonomy as a town only in 1963, after more than one century from its annexation to the Unity of Italy.