Sassari (US: SAH-sər-ee, SAH-sar-ee, Italian: [ˈsassari] (listen); Sassarese: Sàssari [ˈsasːari]; Sardinian: Tàtari [ˈtataɾi]) is an Italian city and the second-largest of Sardinia in terms of population with 127,525 inhabitants, and a Functional Urban Area of about 260,000 inhabitants. One of the oldest cities on the island, it contains a considerable collection of art.

Since its origins at the turn of the 12th century, Sassari has been ruled by the Giudicato of Torres, the Pisans, as an independent republic in alliance with Genoa, by the Aragonese and the Spanish, all of whom have contributed to Sassari's historical and artistic heritage. Sassari is a city rich in art, culture and history, and is well known for its palazzi, the Fountain of the Rosello, and its elegant neoclassical architecture, such as Piazza d'Italia (Italy Square) and the Teatro Civico (Civic Theatre).

As Sardinia's second most populated city, it has a considerable amount of cultural, touristic, commercial and political importance in the island. The city's economy mainly relies on tourism and services, however also partially on research, construction, pharmaceuticals and the petroleum industry.