Early 21st century
The modern lingua franca, as we call it in English (from the Italian for "French,") is English. It is the pre-eminent international language. There are many that are international regionally, but English is the first global common tongue. It is currently the first language in business, aviation, science, and technology (and, via that technology, on the internet.)
In matters of international diplomacy, English has "partially displaced" French which is a diplomatic way of saying "has replaced."
The etymology of "lingua franca," in reality, is more complicated than "'the French language' in old Italian." The original Lingua Franca was a pidgin tongue, a simplification and amalgamation that was used widely in eastern Mediterranean commercial and political transactions.
The name of that ad hoc trade language was a misnomer, likely based upon a tendency of merchants in that realm to generalize the European idioms as "Frankish."