Gas giants, also known as gas planets, were large and massive planets composed chiefly of various gases. They had no solid, well-defined surface, which rendered them uninhabitable in themselves, but at least some of them had a large number of moons. Typically, gas giants harbored little life unless their atmosphere comprised a layer capable of supporting oxygen-breathing species. Atmospheres such as these could also harbor turbulent storms within, such as the case with the planet Wynkahthu. Another characteristic of those worlds was the presence of planetary rings made up of several million pieces of debris. In some cases, those debris were rocky in nature and rich in ore.
Due to their significant masses, such planets had gravity wells that created distinct, if minor, hazards for hyperspace travel. Under certain circumstances, a particularly enormous gas giant could become a star in its own right.
Ajara, Bespin, Endor, Jestefad, Lefrani, Galaan, Hudalla, Noctu, Pujool, Cavas, Kol Iben, Golus, and Yavin were all gas giants. The feature that distinguished Bespin from most of its sister planets was the existence of its oxygen-rich Life Zone, which possessed an unusual abundance of life forms and included Cloud City.