Sør-Frøya is a former municipality in the old Sør-Trøndelag county, Norway. The 102-square-kilometre (39 sq mi) municipality existed from 1906 until its dissolution in 1964. Sør-Frøya included the southwestern part of the island of Frøya in what is now the municipality of Frøya in Trøndelag county. The main population center of Sør-Frøya was the village of Titran on the western tip of the island. The main church for the municipality was Hallaren Church which is located in Storhallaren on the southern coast of the island.

Frøya is the westernmost municipality in Trøndelag county, Norway. It is part of the Fosen region and consists of the island of Frøya, which lies north of the island of Hitra, as well several thousand other small islands surrounding the island of Frøya. The village of Sistranda is the administrative center of Frøya. Other villages include Hammarvika, Titran, Sula, and Mausund. The main island of Frøya is connected to the neighboring island of Hitra by the Frøya Tunnel which goes under the Frøyfjorden.