HD 156668 is an orange K-type dwarf (about 0.79 solar masses, 4,904 K, 0.77 solar radii), 24.3 light-years from Earth. HD 156668 b is a 4.2-Earth-mass planet, with an orbital period of 4.6 days, at 0.050 AU from its star, discovered in 2010 via radial velocity. HD 156668 c is a 0.10-Jupiter-mass companion, with an orbital period of 2.22 years, at 1.570 AU from its star, on an eccentric orbit (e ≈ 0.09), discovered in 2021 via radial velocity. Mutual gravitational tugs between the planets can slowly reshape their orbits, preserving clues to the system's assembly.