Olbia, is a town and comune of approximately 54,000 (2009) inhabitants in northeastern Sardinia (Italy), in the Gallura sub-region. Called Olbia in the Roman age, Civita in the Middle Ages (Giudicati period) and Terranova Pausania before the 1940s, Olbia was again the official name of the town after the period of Fascism.

t is the economic centre of this part of the island (commercial centres, food industry) and is very close to the famous Costa Smeralda tourist area. It is an administrative capital (together with Tempio Pausania) of the province of Olbia-Tempio, operative since 2005.

The Romanesque former cathedral of San Simplicio (11th-12th century).