Italian astronomer who in 1801 identified the first asteroid, which he named Ceres.
Piazzi was born in Ponte di Valtellina (now in Switzerland). He studied in various Italian cities and in 1764 entered the Theatine Order as a monk. In 1779 he became professor of mathematics at the Palermo Academy in Sicily. When it was decided to establish observatories in Palermo and Naples, Piazzi travelled to observatories in England and France to obtain advice and equipment. He was director of Palermo Observatory from 1790 and from 1817 also of Naples Observatory. Additional responsibilities included the reformation of the Sicilian system of weights and measures 1812.
In 1803, Piazzi published his first catalogue of fixed stars, which located 6,748 stars with unprecedented accuracy.