It is distinguished by its highly irregular shape, chaotic rotation, low density, and its unusual sponge-like appearance.

Hyperion's discovery came shortly after John Herschel had suggested names for the seven previously known satellites of Saturn in his 1847 publication Results of Astronomical Observations made at the Cape of Good Hope.

[16] Hyperion is one of the largest bodies known to be highly irregularly shaped (non-ellipsoidal, i.e. not in hydrostatic equilibrium) in the Solar System.

A possible explanation for the irregular shape is that Hyperion is a fragment of a larger body that was broken up by a large impact in the distant past.

[18] Like most of Saturn's moons, Hyperion's low density indicates that it is composed largely of water ice with only a small amount of rock.

It is thought that Hyperion may be similar to a loosely accreted pile of rubble in its physical composition.

However, unlike most of Saturn's moons, Hyperion has a low albedo (0.2–0.3), indicating that it is covered by at least a thin layer of dark material.

Hyperion's surface is covered with deep, sharp-edged craters that give it the appearance of a giant sponge.

The reddish substance contains long chains of carbon and hydrogen and appears very similar to material found on other Saturnian satellites, most notably Iapetus.

[19] The latest analyses of data obtained by Cassini during its flybys of Hyperion in 2005 and 2006 show that about 40 percent of it is empty space.