TOI-3757 is a cool M-dwarf (about 0.64 solar masses, 3,913 K, 0.62 solar radii), 181 light-years from Earth. TOI-3757 b is a 0.27-Jupiter-mass companion, with an orbital period of 3.4 days, at 0.038 AU from its star, and an equilibrium temperature near 759 K, on an eccentric orbit (e ≈ 0.14), discovered in 2022 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.