On March 17th, 1861 the Italian Kingdom was born. However, some Italian regions were annexed to the Kingdom only afterward: Veneto was annexed in 1866, Trentino Alto Adige, Friuli Venezia Giulia, Istria, Zara in 1920 and the city of Fiume only in 1924.
Although there are no limitations of generations to apply for Italian citizenship by descent, the Italian ancestor (the last ascendant born in Italy), in order to transmit Italian citizenship, had to be born after the date of annexation of his region of birth.
If the birth of the Italian ancestor occurred before the unification of Kingdom of Italy and if he moved abroad, you have to check the date of his death: if the death occurred before the proclamation of the Kingdom of Italy, the descendants never acquired Italian citizenship; if the death occurred after the date of annexation of the region of birth, the ancestor died as an Italian citizen and was able to transmit the citizenship to his direct descendants.
Avv. Paola Caputi