Kepler-138, also known as KOI-314, is a red dwarf located in the constellation Lyra, 219 light years from Earth. It is located within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission used to detect planets transiting their stars.

A Mini-Neptune is a planet less massive than Neptune but resembling Neptune in that it has a thick hydrogen-helium atmosphere, probably with deep layers of ice, rock or liquid oceans.