The planet Jupiter was named after the chief Roman god of the same name, also known as Jove. It was named so because Jupiter is the largest planet in the solar system, while Jove is the king of the Roman gods.
Most of Jupiter's known satellites, such as the Gallilean moons, are also named after Roman mythological figures: Io, Europa, Ganymede and Callisto, among others. Interestingly, the ancient Greeks also named this massive planet after the king of their pantheon of deities - the fiery Zeus. Four planets form a group that astronomers call the Jovian planets, which include Jupiter, Saturn, Uranus and Neptune.