Kepler-128 is a Sun-like F-type star (about 1.18 solar masses, 6,072 K, 1.66 solar radii), 396 light-years from Earth. Kepler-128 b is a 3.8-Earth-mass planet, with an orbital period of 15.0 days, discovered in 2013 via transit. Kepler-128 c is a 3.4-Earth-mass planet, with an orbital period of 22.8 days, discovered in 2013 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. Mutual gravitational tugs between the planets can slowly reshape their orbits, preserving clues to the system's assembly.