HD 28109 is a Sun-like F-type star (about 1.23 solar masses, 6,189 K, 1.43 solar radii), 140 light-years from Earth. HD 28109 b is a 6.2-Earth-mass planet, with an orbital period of 22.9 days, and an equilibrium temperature near 867 K, discovered in 2022 via transit. HD 28109 c is a 9.2-Earth-mass planet, with an orbital period of 56.0 days, and an equilibrium temperature near 643 K, discovered in 2022 via transit. HD 28109 d is a 5.8-Earth-mass planet, with an orbital period of 84.3 days, and an equilibrium temperature near 561 K, discovered in 2022 via transit.