1 Ceres (asteroid 1 -- See-reez) was the first asteroid to be discovered, with a diameter of 1003 km, and a surface area of 1,800,000 km². It was discovered on January 1, 1801, by Giuseppe Piazzi, and originally named Ceres Ferdinandea after the Classical Greek and Sicilian goddess of plants and motherly love and King Ferdinand IV of Naples and Sicily. The Ferdinandea part was dropped for political reasons.

Ceres is the largest known asteroid in the traditional asteroid belt between Mars and Jupiter. However, the Kuiper belt is now known to contain at least three larger objects: 28978 Ixion, 50000 Quaoar and 2004 DW. Pluto is also sometimes considered a Kuiper-belt object.

Ceres is unique in that its size and mass are sufficient to give it a spherical shape, much like a planet. Other large asteroids such as Juno and Vesta are known to be distinctly non-spherical. With a mass of 8.7×10²⁰kg, Ceres comprises over one-third the 2.3×10²¹ kg estimated total mass of all the asteroids.

The chemical element Cerium (atomic number 58) was discovered in 1803, two years after Ceres was discovered, and has been named after the asteroid.