Kepler-1391 is a Sun-like G-type star (about 1.03 solar masses, 5,840 K, 1.10 solar radii), 1,038 light-years from Earth. Kepler-1391 b is a planet with 1.7 Earth radii, with an orbital period of 54.4 days, discovered in 2016 via transit. The planet was found when it crossed the face of its star, producing periodic dips in brightness that reveal its size and orbital period to space-based photometry. At 1.7 Earth radii, Kepler-1391 b is a compact world comparable in size to rocky planets in our Solar System.