Born in Rome, Gigli stood out in his youth during his studies, which led him to pursue a doctorate in law. He soon began to write, first an autobiography that he abandoned to begin writing the work that made him most famous, his Memoirs of Giacinto Gigli: Giacinto Gigli's Memoirs of some everyday things that happened in his time, better known as the Roman Diary. Without being a historical work, it provides interesting data and details on the daily life of Rome between 1608 and 1670.

An extensive biography can be found at: Crucitti, Filippo: “GIGLIO, Giacinto ”, en Dizionario Biografico degli Italiani. Vol. 54. Treccani (2000).