boyfriend / fiancé
fidanzati
fee-dan-DZAH-toh
Fidanzato covers both 'boyfriend' and 'fiancé' in Italian. Context clarifies which is meant. 'Fidanzarsi' means to get engaged/start dating. The level of commitment implied depends on the relationship.
Il mio fidanzato si chiama Luca.
My boyfriend is called Luca.
Ci siamo fidanzati a Venezia.
We got engaged in Venice.