How many languages Mezzofanti actually spoke depends on the definition you give to 'speaking a language'. Some languages he spoke like a native speaker, other he could only write.

The author of the book on which this section of the site is based defined a certain standard and arrived at 38 languages we can be certain Mezzofanti spoke fluently, based on written accounts of people such as Lord Byron or the Russian ambassador to Rome who visited Mezzofanti and challenged him in their own language.

This table lists all languages he spoke and how well he knew them.