Formal:
* Viva! (This is the most common and direct translation, literally meaning "long live")
* Evviva! (This is a more enthusiastic exclamation, similar to "hurray!")
* Lunga vita a... (This translates to "Long life to..." and is used to wish long life to someone or something)
Informal:
* Evviva! (As mentioned above, this is also suitable for informal settings)
* Woooo! (This is a very informal and casual way to express excitement, similar to "woohoo!")
Example:
If you wanted to say "Long live the Queen!" in Italian, you would say: "Viva la Regina!"