Ostuni (Barese: Ostune; Salentino: Stune) is a city and comune, located about 8 km from the coast, in the province of Brindisi, region of Apulia, Italy.

The town is reputed to have been originally established by the Messapii, a pre-classic tribe, and was nearly completely destroyed by Hannibal during the Punic Wars.

From 1300 to 1463 it was part of the Principality of Taranto and from 1507 (together with what is now the frazione of Villanova and Grottaglie) passed to Isabella, Duchess of Bari, wife of Gian Galeazzo Sforza, Duke of Milan.

Monuments in their own right, the town's largest buildings are the Ostuni Cathedral and the Bishop's Palace, together with a number of palazzi of local aristocratic families: Aurisicchio, Ayroldi, Bisantizzi, Falghieri, Ghionda, Giovine, Jurleo, Marseglia, Moro, Palmieri, Petrarolo, Sansone, Siccoda, Tanzarella, Urselli and Zaccaria.

In the surrounding countryside there are typical Pugliese "masserie", fortified large estate-farms, one of which, San Domenico, was once held by the Knights of Malta.