Italians will often say "OMG" as "Oh mio Dio!".
Some Italians may say OMG as "Dio Mio!".
Oh mio Dio and Dio Mio in Italian mean "Oh my God!", or "My God!".
The more condensed and common exclamation for "OMG" in Italian is "Oddio!".
Other Italian related phrases for "OMG are Mamma mia, which expresses a range of emotions that are similar to "Oh my God", and in Italian, "Madonna!" is used for showing surprise or amazement.