GJ 2126 is a cool M-dwarf (about 0.65 solar masses, 4,159 K, 0.73 solar radii), 38.1 light-years from Earth. GJ 2126 b is a 1.30-Jupiter-mass companion, with an orbital period of 273 days, at 0.710 AU from its star, on an eccentric orbit (e ≈ 0.85), discovered in 2025 via radial velocity. The planet betrayed itself through the star's reflex motion — a technique that first revealed worlds around Sun-like stars in the 1990s and remains a workhorse of exoplanet discovery. The planet's marked eccentricity suggests past scattering events or perturbations from unseen companions.