Gas giant
The smallest known extrasolar planet that is likely a "gas planet" is Kepler-138d, which has the same mass as Earth but is 60% larger and therefore has a density that indicates a thick gas envelope.
Mini-Neptune
A mini-Neptune or sub-Neptune (sometimes known as a gas dwarf or transitional planet) is a planet of up to 10 Earth masses (), less massive than Uranus and Neptune, which have about 14.5 and 17 , respectively. Mini-Neptunes 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).