Could gas giants be considered stars that failed to ignite?

Maybe. It depends on what gas giant youò??re looking at and how you distinguish a ò??planetò?? from a ò??failed star.ò?? A gas giant found in orbit around a star might be considered a planet like Jupiter around the Sun. An isolated gas giant is probably a failed star. A failed star has such a low mass that its core never gets hot enough to fuse hydrogen, although it might fuse other elements like lithium and deuterium. A planet has an even lower mass and thus never fuses anything.