TOI-561 is a Sun-like G-type star (about 0.81 solar masses, 5,342 K, 0.84 solar radii), 85.8 light-years from Earth. TOI-561 is an ancient thick-disk star, about 10 billion years old, with an ultra-short-period rocky planet. TOI-561 b is a 2.0-Earth-mass planet, with an orbital period of 10.7 hours, at 0.011 AU from its star, and an equilibrium temperature near 2,319 K, discovered in 2020 via transit. TOI-561 c is a 5.9-Earth-mass planet, with an orbital period of 10.8 days, at 0.089 AU from its star, and an equilibrium temperature near 802 K, discovered in 2020 via transit. With 4 confirmed worlds, TOI-561 is a densely packed system whose resonances, spacing, and formation history are active research topics.