Italian was a language which originated in Italy.
The Fourth Doctor and Sarah Jane Smith spoke Italian when they travelled to San Martino in 1492. (TV: The Masque of Mandragora)
The Seventh Doctor mocked the Gods of Ragnarok, saying, "La commedia è finita". (TV: The Greatest Show in the Galaxy)
One of the catchphrases of the Tenth Doctor was "Molto bene!", which was also quoted by Donna Noble. (TV: Midnight, Journey's End) On one occasion, he also added "Bellissimo!" (TV: Planet of the Ood)
Contacting a fellow Slitheen operative stationed in Naples, Glune Fex Fize Sharlaveer-Slam Slitheen exclaimed "Grazie, Napoli." (TV: Revenge of the Slitheen)
By 1927, Jack Harkness was not fluent enough in Italian to understand Mrs Giardano when she spoke it. Being Angelo Colasanto's native language, he translated for Jack. (TV: Immortal Sins)
By the 26th century, Italian was a nearly-lost language. (PROSE: The Dimension Riders)