A Mini-Neptune (also sometimes called a 'gas dwarf') is a planet, smaller in size to Uranus or Neptune, but has 10 or more Earth masses. hose planets have thick hydrogen-helium atmospheres, probably with deep layers of ice, rock or liquid oceans (made of water, ammonia, a mixture of both, or heavier volatiles).

Several extrasolar planets which may be gas dwarfs have been discovered, based on known masses and densities. For an example Kepler-11f has a mass of 2.3 Earths, but has a density which is similar to Saturns, which would imply that the planet is a gas dwarf, with a liquid ocean surrounded by thick hydrogen-helium atmosphere and only a small rocky core. These planets do not orbit too close to it's host parent star, otherwise that thick atmosphere would be blown away by stellar winds.