Who had a masterpiece in the Italian vernacular?

Dante Alighieri (between May 22 and June 13, 1265 - September 14, 1321) wrote the masterpiece "Divina Commedia" ("The Divine Comedy") in the Italian vernacular.

Specifically, Dante's complete name is Durante di Alighiero degli Alighieri. The Italian poet is considered the "Father of the Italian language" because his poetic masterpiece was written in the Florentine form of Italian that he grew up speaking. At the time, literature still was being written in Latin.