Fanzago was born in Clusone in a family of bronze-casters and architects. In 1608, after a short stay in Chieti, he moved to Naples. Here he trained as a marble sculptor and mason under the Tuscan sculptor Angelo Landi. His first important work was the sepulchre monument of Mario Carafa, a relative of Cardinal Carafa. His architectural debut was the design of San Giuseppe dei Vecchi a San Potito. According to an essay about Fanzago's life by count Fogaccia, in Naples he obtained the support of the Benedictines, the Viceroy Duke of Medina, Prince Caracciolo and the Carthusians, and soon opened a workshop of his own. Apparently he sympathised with Masaniello's revolt, and after the return of Royal authority, Fanzago was sentenced to death and had to flee to Rome, where he worked for a decade. He returned to Naples and designed the initial layout church of Santa Maria Egiziaca a Pizzofalcone. This church displays a Greek cross plan, and resembles a hybrid of contemporary Baroque masterpieces by Bernini and Borromini. He also designed the church of Santa Teresa a Chiaia. His last great church was Santa Maria Maggiore, built between 1653 and 1675. Fanzago died at an age of 87 years. One of his pupils was Lorenzo Vaccaro.
Main works in Naples
His works in Naples include:
Guglia di San Gennaro: a votive spire in honor of the patron saint of Naples. It imitates the large portable ephemeral decorations common in religious processions
model for two other prominent spires, which he helped plan. It was a so-called "plague column"; that is, a spire built in thanks for having been spared from the recent epidemic.
Extensive work on the Certosa di San Martino, including the spectacular central courtyard with its large portals and busts of Carthusian saints. The church and cloisters are considered to be his masterpiece. The Carthusians paid Fanzago 57,000 ducats over 33 years of work. Between 1660 and 1700, a lawsuit alleging underpayment by the monks wound its way through the Neapolitan courts.
The facades or facade details of numerous churches, chapels, and civic buildings, including Santa Maria degli Angeli, anonymous works within the Cathedral of Naples, the Chiesa dell'Ascensione a Chiaia ; the facade of Santa Maria della Sapienza ; the bronze gate of the chapel of the royal treasury; and the original design for church of San Francesco Saverio ;