Sassarese (natively sassaresu [sasːaˈrezu] or turritanu; Sardinian: tataresu [tataˈɾezu]) is an Italo-Dalmatian language and transitional variety between Sardinian and Corsican. It is regarded as a Corso–Sardinian language because of Sassari's historic ties with Tuscany and geographical proximity to Corsica. Despite the robust Sardinian influences (in terms of vocabulary and phonology, as well as syntax), it still keeps its Corsican (and therefore Tuscan) roots, which closely relate it to Gallurese; the latter is linguistically considered a Corsican dialect despite its geographical location, although this claim is a matter of controversy. It has several similarities to the Italian language, and in particular to the old Italian dialects from Tuscany.

Sassarese is spoken by approximately 100,000 people, out of a total population of 175,000, in the northwest coastal areas of Sardinia, Italy. Large Sassarese-speaking communities are present in Sassari, Stintino, Sorso, and Porto Torres. The Sassarese varieties transitioning to Gallurese, known as the Castellanesi dialects, can be heard in Castelsardo, Tergu, and Sedini.

Sassarese emerged as an urban lingua franca in the late part of the age of the Judicates (13th–14th century), based on a mixture of different languages – namely Sardinian, Corsican/Tuscan, and Ligurian. The neighbouring Logudorese dialects of Sardinian exercised a significant influence on the modern linguistic development, along with some Catalan and Spanish vocabulary. There exist many modern and older works both on and in Sassarese, and a number of cultural, social, and theatre events are held regularly in connection with it.

In 1943 the German linguist Max Leopold Wagner wrote:

... A vernacular which, by all indications, was gradually formed from the 16th century, after several very deadly plagues decimated the city's population; the bulk of the survivors were of Pisan and Corsican origin, there were even Genovese. Thus, this hybrid dialect was born, and is now spoken in Sassari, Porto Torres and Sorso, whose base is Tuscan-shifted with traces of Genovese, in addition to not a few Sardinian words.