The Jovian planets are Jupiter, Saturn, Uranus, and Neptune. They orbit far from the sun. These planets have no solid surfaces and are essentially large balls of gas composed primarily of hydrogen and helium. They are much larger than the terrestrial planets (Earth, Mercury, Venus, and Mars).

In our solar system, the Jovian planets share two main characters: they are comprised of gaseous matter, rather than solid rock, and are very large relative to the other, terrestrial planets. The four Jovian plants in the solar system--Jupiter, Saturn, Uranus, and Neptune--are all classified as "gas giants," meaning that they are made out of gases, rather than the solid materials that comprise the "terrestrial" planets (such as Earth). The gas giants are also much larger than the four terrestrial planets. In fact, the mass of the planet Jupiter can hold about 1,300 Earth-sized planets. The term "Jovian" comes from the planet Jupiter (as "Jove" is an alternate name for the Roman god Jupiter), which is the largest planet in our solar system.