K2-45 is an orange K-type dwarf (about 0.50 solar masses, 4,103 K, 0.45 solar radii), 495 light-years from Earth. K2-45 b is a planet with 6.7 Earth radii, with an orbital period of 1.7 days, at 0.022 AU from its star, 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. K2-45 b skims its star closer than Mercury orbits the Sun. Repeated transit observations constrain the planet's orbital inclination and stellar density, anchoring the system's physical scale.