Kepler-1321 is an orange K-type dwarf (about 0.54 solar masses, 4,094 K, 0.53 solar radii), 769 light-years from Earth. Kepler-1321 c is a planet with 2.4 Earth radii, with an orbital period of 2.2 days, discovered in 2016 via transit. Kepler-1321 d is a planet with 2.6 Earth radii, with an orbital period of 5.7 days, discovered in 2021 via transit. Kepler-1321 b is a planet with 4.9 Earth radii, with an orbital period of 11.1 days, discovered in 2016 via transit. Mutual gravitational tugs between the planets can slowly reshape their orbits, preserving clues to the system's assembly.