The paper sketches the history of the linguistic unification of Italy, in its first phase under the influence of the great Florentine poets and writers of the 14th century (Dante, Petrarca, Boccaccio), and during the 16th century under the influence of the grammarians, in particular Pietro Bembo, who was responsible for the victory of Florentine Italian over its competitors in the debate over the literary standard. From the 17th century onwards the Accademia della Crusca, with its famous Dictionary which followed Bembo’s lead and which was based on Florentine texts from the 13th to the 16th centuries, established itself as the guide and model of the Italian literary language. The author of this paper describes in the following the both positive and negative consequences of the Dictionary which, having become an indispensable instrument for authors writing in Italian, imposed on them a rigorous linguistic purism though, on the other hand, it vigorously contributed to the unity of the literary language. In modern times, especially following the political unification of Italy, the new demands for a standard both of written and spoken language truly shared by the entire people, could no longer be satisfied by the literary purism espoused by the Accademia della Crusca. The paper concludes by a description of the linguistic situation in late 19th-century Italy and the role being played by the Accademia, which has by now become a centre of activity which can be characterized as truly scientific in the modern sense of the term, and which has launched the new Historical Dictionary of the Italian language.