Tertenia is a comune (municipality) in the Province of Ogliastra in the Italian region Sardinia, located about 100 kilometres (62 mi) northeast of Cagliari and about 25 kilometres (16 mi) south of Tortolì.

Tertenia borders the following municipalities: Cardedu, Gairo, Jerzu, Lanusei, Loceri, Osini, Ulassai.

It is located in a high valley at the base of Mt. Arbu and Mt. Ferru, along the Rio Quirra river.