Portoscuso (Portescusi in Sardinian) is a comune (municipality) in the Province of South Sardinia in the Italian region Sardinia, located about 75 kilometres (47 mi) west of Cagliari and about 14 kilometres (9 mi) northwest of Carbonia.

Portoscuso borders the following municipalities: Carbonia, Gonnesa, and San Giovanni Suergiu.

Bronze Age sites include the ruins of several Nuraghe (e.g. Baccu Ollasta) and the rock shelter of Punta Niedda, where the bones of 6 individuals and various objects of the Bonnanaro culture were recovered in the 1940s.

The town is extremely proud of its famous tuna fishery, and is restoring the original buildings.

As of 2023 Portoscuso is the municipality with the highest per capita income in the province of South Sardinia, equal to 19,600€.