Which planet is considered a gas giant?

Jupiter is considered a gas giant because it primarily consists of hydrogen and helium and lacks a well-defined solid surface. Gas giants, such as Jupiter, have thick atmospheres and significant mass, allowing them to retain large amounts of gas. This classification is in contrast to terrestrial planets like Earth, Mercury, and Mars, which are primarily composed of rock and metal and possess solid surfaces. Jupiter's immense size, along with its extensive system of moons and rings, further emphasizes its distinction as a gas giant in our solar system.