French is the only official—and by far the most common—language in Monaco, a result of the role France has had over the microstate, since the annexation of Nice and the Nizzardo (the territory surrounding Monaco).
Monégasque is the traditional national language of the Monegasque people (who represent only 21.6% of the total population). It is a dialect of Ligurian, and is somewhat similar to Italian.
Because the Monégasques are only a minority in Monaco, their tongue was threatened with extinction in the 1970s. However, the language is now being taught in schools. In the old part of Monaco, the street signs are marked with Monégasque in addition to French.
There is also an Anglophone community in Monaco (8.5% of which are from the United Kingdom or the United States, with English-speakers from other nations as too insignificant and thus listed within the category of "other," below), in addition to English-speaking tourists visiting the city.
Princess Grace was born an American, and all three of her children (including the reigning Prince) grew up speaking English among other languages.