The history of the modern Italian language is complicated, but was shaped largely by relatively recent events. The earliest surviving texts which can definitely be called Italian are legal formulae from Benevento region, dating from 960-963 A.D. Italian was formalised in the early 14th century through the works of Dante Alighieri, who mixed southern Italian languages, especially Sicilian, with Tuscan in his poems known collectively as the Commedia. Alighieri's great works were read throughout Italy, and so his written dialect soon became the standard that others could all understand. Thus is Alighieri credited with standardizing the Italian language.

Like so many other languages, there have always been distinct dialects for each Italian city, since the cities were up until recently city-states. A well-known Italian dictum holds that the best spoken Italian is lingua toscana in bocca romana, "the Tuscan tongue, with a Roman accent". The Romans are known for speaking clearly and distinctly, while the Tuscan dialect (supposedly influenced by Etruscan and Oscan) is the closest existing dialect to Dante's now-standard Italian.

In contrast to the dialects of northern Italy, the older southern Italian dialects have remained largely untouched by other European influences during the middle ages. The economic might and relative advanced development of Tuscany at the time gave its dialect weight, although the Venetian dialect remained widespread in medieval Italian commercial life. Also, the increasing cultural relevance of Florence during the Renaissance made its dialect a standard in the arts.