10 Hygiea is a large asteroid in the outer region of the main asteroid belt, between the orbits of Mars and Jupiter. It was the tenth known asteroid, discovered on 12 April 1849 by Italian astronomer Annibale de Gasparis at the Astronomical Observatory of Capodimonte in Naples, Italy. It was named after Hygieia, the Greek goddess of health. It is the fourth-largest main-belt asteroid by both volume and mass, with a mean diameter of 433 km (269 mi) and a mass constituting 3% of the main asteroid belt's total mass.