Giuseppe Piazzi (July 16, 1746 – July 22, 1826) is an Italian Catholic priest of the Theatine order, mathematician, and astronomer.

He was born in Ponte in Valtellina, and dies in Naples.

He establishes an observatory at Palermo, now the Osservatorio Astronomico di Palermo – Giuseppe S. Vaiana.

Perhaps his most famous discovery is the first dwarf planet, Ceres.