Chiesa di Santa Maria Assunta, Romanesque church in Monteriggioni, Italy

The Chiesa di Santa Maria Assunta is a single-nave rectangular church with a small square apse, covered by barrel vaults with lunettes. Its facade, completed by 1235, is built of golden travertine blocks and has an oculus above the portal. The portal combines a Florentine-style outer arch with a Pisan-style molded ring, and the north side has two double-splayed windows and two portals, one walled up.

The church was built between 1213, the year Monteriggioni was founded, and 10 June 1235, when delegates of Siena and Poggibonsi accepted peace terms with Florence inside it. At the end of the 13th century it was raised to pieve, receiving the title of the canonica of Santa Maria di Stomennano and a baptismal font. In 1360 the statutes of Siena fixed its piviere at ten suffragan churches; the building was partly altered in the first half of the 19th century.

The church appears as Monteriggioni in the Assassin's Creed II and Brotherhood video games, set in the late 15th to early 16th century and in 2012. Until the early 14th century the building hosted civil as well as religious functions, and in 1313 the abbot of Isola, lord of the surrounding lands, regularly sat here.

The church stands on Monteriggioni's main square, facing the travertine facade with its oculus above the portal. The bell tower from the 18th century rises at the northern corner of the apse. The building was partly altered in the first half of the 19th century, so the interior vaults differ from the medieval work.

The bell still hanging in the church was placed there in 1299 and may have come from the castle fortress; it is not the only gift, since the Republic of Siena donated another bell in 1298. The church also keeps a wooden crucifix and two 15th-century tabernacles.