Kepler-1666 is a Sun-like F-type star (about 1.23 solar masses, 6,293 K, 1.15 solar radii), 1,379 light-years from Earth. Kepler-1666 b is a planet with 2.9 Earth radii, with an orbital period of 25.8 days, discovered in 2020 via transit. Kepler-1666 c is a planet with 3.2 Earth radii, with an orbital period of 40.7 days, discovered in 2020 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.