Oschiri (Gallurese: Óscari, Sardinian: Óscheri) is a comune (municipality) and former bishopric in the Province of Sassari in the Italian region Sardinia, located about 170 kilometres (110 mi) north of Cagliari and about 40 kilometres (25 mi) southwest of Olbia.

Oschiri borders the following municipalities: Alà dei Sardi, Berchidda, Buddusò, Ozieri, Pattada, Tempio Pausania, Tula.

The bishopric dates back to Byzantine times (circa 1000 AD), but the earliest mention of a bishop of Castro is of 1116, when an unnamed bishop of the see assisted at the dedication of the Basilica di Saccargia.

In 1164, its bishop Atto dedicated a church in the locality of Aneleto and granted it in the following year to Camaldolese monks.

It has had the following incumbents, both of the lowest (episcopal) and intermediary (archiepiscopal) ranks : Titular Archbishop Giuseppe Pittau, Jesuits (S.J.)