Ennio Quirino Visconti (November 1, 1751 – February 7, 1818) was an Italian antiquarian and art historian, papal Prefect of Antiquities, and the leading expert of his day in the field of ancient Roman sculpture. His son, Pietro Ercole Visconti, edited Versi di Ennio Quirino Visconti, raccolti per cura di Pietro Visconti while Louis Visconti became a noted architect in France. His brother, Filippo Aurelio Visconti (died 1830) was also a classical scholar, who published the Museo Chiaramonti, a successor to the Museo Pio-Clementino.
Born in Rome, he was the son of Giovanni Battista Antonio Visconti (1722–1784), the curator of Clement XIV, who reorganised and restored the papal collection of antiquities, as the Museo Pio-Clementina. Appointed by Pope Pius VI to succeed his father in the position, the brilliant and precocious Visconti took up his father's position as conservator of the Capitoline Museums in Rome in 1787; he assisted his father in producing the first volume of the Museo Pio-Clementino (1782) and produced the six remaining volumes himself, completing the last in 1807; this catalogue of the Roman sculpture and antiquities in the Vatican collections, published in the course of many years, "made an impact on archaeological studies second only to that of Winckelmann." He also published the antiquities collected in Greece by Sir Richard Worsley in Museum Worsleyanum (1794) and the sculptures in the Villa Borghese, (1796).
In 1798, he became one of five consuls of the short-lived Roman Republic. With the restoration of papal control in Rome he had to emigrate to Paris, where his presence was most welcome: "this event we considered as one of the happiest results of our victories", wrote the antiquary Aubin-Louis Millin de Grandmaison. At the end of 1799 he became curator of antiquities of the Musée Napoleon housed in the Louvre, many of which were familiar to him as booty removed under the stipulations of the Treaty of Tolentino (1796); his descriptions were published by Robillard-Perronville in Le Musée français; In 1803 he was made professor of archaeology at the Institut de France. In Paris he published a series of portraits of famous men of Antiquity: Iconographie Grecque, 3 vols. 1808, and a first volume of Iconographie Romaine, 1818. At his death, extended obituaries were published by Quatremère de Quincy and others.