Kepler-1978 is a Sun-like G-type star (about 0.87 solar masses, 5,251 K, 0.78 solar radii), 866 light-years from Earth. Kepler-1978 b is a planet with 2.7 Earth radii, with an orbital period of 10.8 days, at 0.091 AU from its star, and an equilibrium temperature near 676 K, discovered in 2023 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. Kepler-1978 b orbits well inside Earth's distance from the Sun.