Seggiano is a comune (municipality) in the Province of Grosseto in the Italian region Tuscany, located about 100 km south of Florence and about 40 km northeast of Grosseto. It has a population of 982 and an area of 49.6 km².

Seggiano borders the following municipalities: Abbadia San Salvatore, Castel del Piano, Castiglione d'Orcia.

Near Seggiano is the Giardino di Daniel Spoerri, a sculpture garden by the artist Daniel Spoerri.

This town was founded at the begining of 1000 as a hamlet of Abbazia di San Salvatore at Monte Amiata which after this year made part of the rights of the Abbazia di Sant'Antimo.

It was under Senese government until about the midst of 1200 in which years it had lots of influences of the family Salimbeni. This until 1300 and afterwards came the Ugurgeri which stayed from 1400 and on. Seggiano was part of the Siena Republic until 1555 and came then under the Granducato di Toscana.

Seggiano has its own website.