HD 164509 is a Sun-like G-type star (about 1.12 solar masses, 5,859 K, 1.11 solar radii), 53.1 light-years from Earth. HD 164509 b is a 0.44-Jupiter-mass companion, with an orbital period of 280 days, at 0.870 AU from its star, on an eccentric orbit (e ≈ 0.24), discovered in 2012 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.