HD 111591 is an orange K-type dwarf (about 1.94 solar masses, 4,884 K, 8.03 solar radii), 114 light-years from Earth. HD 111591 b is a 4.40-Jupiter-mass companion, with an orbital period of 2.89 years, at 2.500 AU from its star, on an eccentric orbit (e ≈ 0.26), discovered in 2017 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.