- a name given to Hades, under which he is identified by the Romans with Orcus.
- a dwarf planet having an equatorial diameter of about 2,100 miles (3,300 km), a mean distance from the sun of 3.674 billion miles (5.914 billion km), a period of revolution of 248.53 years, and one known moon, Charon. Based on the definition of a planet devised by the International Astronomical Union in 2006, Pluto, regarded as the ninth and most distant planet in our solar system since its discovery in 1930, was reclassified as a dwarf planet, a decision that continues to be examined and questioned by some astronomers.
- the god of the underworld; Hades
- the second-largest dwarf planet in the solar system, located in the Kuiper belt; discovered in 1930 by Clyde Tombaugh (1906–97); classified as a planet until 2006, when it was reclassified as a dwarf planet. It has a diameter of 2390 km
- the code name of pipelines laid under the English Channel to supply fuel to the Allied forces landing in Normandy in 1944
