KOI-1257 is a Sun-like G-type star (about 0.99 solar masses, 5,520 K, 1.13 solar radii). KOI-1257 b is a 1.45-Jupiter-mass companion, with an orbital period of 86.6 days, at 0.382 AU from its star, and an equilibrium temperature near 511 K, on an eccentric orbit (e ≈ 0.77), discovered in 2014 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. The planet's marked eccentricity suggests past scattering events or perturbations from unseen companions.