The discussion on this forum may be useful:
It seems that there's some variation depending on which part of Italy you're in, but a long-term partner (whether actually engaged or not) is likely to be referred to as fidanzato or fidanzata, while mio ragazzo or mia ragazza is used for a casual relationship (or by someone with commitment issues!).
Thanks Madelyn. I was wondering why it did not accept fiance as well, I had no idea they were different words. I just received my first French lesson! :)
I wonder though.. can anyone discern the difference in pronunciation between fiance & fiancee, when used in English?.