What class of giant planet is Jupiter?

Jupiter is a gas giant.

Jupiter belongs to the gas-giant class because it is composed mainly of hydrogen and helium rather than having a solid, rocky surface like Earth. It is the largest planet in the Solar System and the fifth planet from the Sun. Its enormous mass creates pressures that transform hydrogen deep inside the planet into electrically conducting metallic hydrogen.

“Gas giant” is a useful planetary classification, but it can be misleading. Much of Jupiter’s interior is not ordinary gas: under immense pressure, hydrogen becomes dense fluid matter, including a metallic phase. The term refers mainly to the planet’s composition and its hydrogen-helium-dominated structure.

Jupiter is commonly confused with an ice giant because both are large outer planets. The Solar System’s gas giants are Jupiter and Saturn, while Uranus and Neptune are classified as ice giants because they contain much larger proportions of water, ammonia, and methane. Jupiter also differs from terrestrial planets through its thick atmosphere, rapid rotation, powerful magnetic field, and lack of a conventional solid surface.