Tratalias is a comune (municipality) in the Province of South Sardinia in the Island of Sardinia, located about 50 kilometres (31 mi) southwest of Cagliari and about 8 kilometres (5 mi) southeast of Carbonia.

Tratalias borders the following municipalities: Carbonia, Giba, Perdaxius, Piscinas, San Giovanni Suergiu, Villaperuccio.

The former cathedral of Santa Maria di Monserrato is an example of Sardinian Romanesque architecture.

Built in 1213–82, it has a façade with two rows of Lombard bands and a rose window.

The interior has a rectangular plan with a nave and two aisles, and a semicircular apse.