In Italian, proper nouns usually do not require the definite article:
Daniele è un bravo ragazzo.
Daniel is a good boy.
Tra poco verrà Mario.
Mario will soon arrive.
Ho scritto a Paola.
I wrote to Paola.
NOTE: nouns are preceded by the article only in northern Italian regional usage: Ho visto la Carla (I saw Carla); Telefono alla Pina (I phone Pina).
However, Italian proper nouns take the article when used in a metaphorical sense:
Si sta rappresentando l'Otello.
He is performing the part of Othello.
l'imperatore Augusto—the emperor Augustus
l'astuto Ulisse—the wily Odysseus.
The surnames of women require the article (la Duse, la Deledda, la Serao), as do Italian surnames in the plural (gli Sforza, i Malatesta, i Visconti).
With men's surnames in the singular, the use of the article is not uniform in the spoken language, and increasingly also in the written; the article is usually omitted and therefore the sentence construction: Ho incontrato Rossi is more common than Ho incontrato il Rossi (I met Rossi).
The use of the article before surnames is maintained in bureaucratic language and news stories:
Dopo la cattura del Ferri e del Binazzi la pericolosa banda di rapinatori è stata sgominata.
After the capture of Ferri and Binazzi the dangerous band of robbers was routed.
In recent years, especially in the political, social, and cultural areas, the tendency has been to avoid the definite article even before female surnames, to avoid inconsistencies between the genders:
Ho letto le opere di Deledda (della scrittrice Grazia Deledda).
I read the works of Deledda (Grazia Deledda).
Nella tarda mattinata Rossi e Bianchi si sono incontrati per una colazione di lavoro (instead of Rossi e la Bianchi or la signora Bianchi).
In the late morning Rossi and Bianchi met for a working lunch.
Such use is very limited and restricted to specialized settings (such as essays) in which it is not possible to confuse the identity of the person.
Many last names of famous people do not take the article:
Garibaldi, Marconi, Pirandello, Verdi, Colombo.
In front of others, however, the predominant form includes the article:
l'Alfieri, l'Alighieri, l'Ariosto, il Tasso.
The nicknames of famous people may or may not include the article:
(il) Botticelli, (il) Tintoretto.
Nicknames of regional or popular usage always take the article if they are aggettivi sostantivati (substantivized adjectives—that is, they imply and replace the surname):
lo Smilzo, il Guercio, il Rosso
While with nouns the use is not constant:
Ho incontrato Patata (or il Patata).
I met Patata.
The article, however, is always present before country appellatives: l'Astigiano (Vittorio Alfieri).
In some cases a noun can be preceded by the plural definite article or the indefinite article: Sono stati i Cavour, i Mazzini, I Garibaldi a costruire l'unità d'Italia (It was Cavour, Mazzini, and Garibaldi who constructed Italian unity); Per ritrarre questa scena ci vorrebbe un Michelangelo (o il pennello di un Michelangelo)—To portray this scene it would take a Michelangelo (or the brush of a Michelangelo); Crede di essere un Einstein—He believed himself to be an Einstein (i.e., as smart as Einstein).
Here the proper noun ceases to indicate a specific individual and designates a type, or a class of persons, characterized by certain quality or defects. This grammatical device corresponds to the figure of speech antonomasia.
To indicate a work of art the article often prefaces the name of the artist:
Quello è un Picasso
That's a Picasso (a Picasso painting)
Ecco il Carrà di cui ti ho parlato
Here is the Carrà (the Carrà painting) of which I spoke.