KOI-217 is a Sun-like G-type star (about 0.95 solar masses, 5,545 K, 0.86 solar radii), 915 light-years from Earth. KOI-217 b is a planet with 12.4 Earth radii, with an orbital period of 3.9 days, at 0.048 AU from its star, discovered in 2010 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. KOI-217 b skims its star closer than Mercury orbits the Sun. The planet's large radius (12.4 Earth radii) indicates a bloated atmosphere heated by intense stellar radiation.