It was one of the more powerful among the Etruscan 12 city confederation. Chiusi went into the Roman orbit in the 3rd century BC and took part to the Social War.
In 540 AD it was occupied by the Ostrogoths and was later seat of Lombard duchy. From the 11th century it was under the rule of the local bishop, and was later contended by Orvieto and, from 1231, Siena, belonging to the latter until 1556, when it was annexed to the Grand duchy of Tuscany
