Cardinal Borgia belonged to a well known family of Velletri, where he was born, and was a distant relative of the House of Borgia. His early education was controlled by his uncle Alessandro (1682–1764), Archbishop of Fermo. From his youth, Stefano Borgia manifested an aptitude for historical research and a taste for relics of ancient civilizations, a line in which he succeeded so well that, at the age of nineteen, he was received into the Academy of Cortona. He founded a museum in Velletri, in which, during his whole life, he gathered coins and manuscripts, especially Coptic, and which may be considered as his major undertaking and achievement. Such was his passion for antiquities that he is known to have sold his jewels and precious earthenware in order to secure the coveted treasures and have the description of them printed. Borgia placed his scientific collection at the disposal of scholars, regardless of creed and country, and giving them encouragement and support. Paolino da San Bartolomeo, Adler, Zoega, Heeren, and many others were among his enthusiastic friends.
Borgia was not left, however, entirely to his chosen field of activity, but was called to fill several important political positions. Benedict XIV appointed him Governor of Benevento. In 1770 he was made secretary of the Congregation de Propaganda Fide, an office of which he took advantage to acquire antiquities by the help of the missionaries—a help which proved always forthcoming. He was made a cardinal in 1789. In the period of the French invasion Borgia was given charge of Rome by Pius VI (1797–98). After the proclamation of the Republic, he was arrested (1798), but quickly released, whereupon he immediately resumed his studies and work of collecting; soon afterwards he joined Pius VI in Valence, Drôme, and endeavoured to have this pontiff send to Asia and Africa a body of missionaries who would preach the Gospel and gather various monuments.
Cardinal Borgia was a participant in the Papal conclave, 1800, which elected Pope Pius VII. Borgia helped him in the reorganization of the Papal States. In 1801 he was made Rector of the Collegium Romanum, and he was in the retinue of Pius VII when this pontiff went to France to crown the new emperor Napoleon. Having arrived in Lyons, Cardinal Borgia was taken ill and died. After his death his collection of Coptic manuscripts was divided: the non-Biblical manuscripts were taken to Naples and placed in the Biblioteca Borbonica, now the Biblioteca nazionale Vittorio Emanuele III; and the Biblical manuscripts, except for a few which were taken to Naples by mistake, given to the Congregation de Propaganda Fide, together with the collection of coins and monuments forming the Museo Borgiano.
At the turn of the Twentieth century the manuscripts of the Museo Borgiano were transferred to the Vatican Library, where they are to be found today. Before the partition of the manuscripts was made the scholar and convert, Jörgen Zoega, wrote a complete and accurate description of them in his posthumous work Catologus Codicum Copticorum manu scriptorum qui in Museo Borgiano Velitris adservantur (Rome, 1810). Borgia also published several works bearing especially on historical topics: Monumento di papa Giovanni XVI (Rome, 1750); Breve istoria dell antica città di Benevento (ibid., 1763–69); Vaticana confessio B. Petri chronoligcis testimoniis illustrata (ibid., 1776); De Cruce Vaticanâ (ibid., 1779); De Cruce Veliternâ (ibid., 1780; Istoria del dominio temporale della Sede Apostolica nelle Due-Sicilie (ibid., 1788).
- Cf. Ciasca, Fragmenta Copto-Sahidica, I, p.xvii