TOI-5143 is an orange K-type dwarf (about 0.86 solar masses, 5,183 K, 0.85 solar radii), 181 light-years from Earth. TOI-5143 c is a planet with 16.3 Earth radii, with an orbital period of 5.2 days, at 0.056 AU from its star, discovered in 2025 via transit. The planet was found when it crossed the face of its star, producing periodic dips in brightness that reveal its size and orbital period to space-based photometry. TOI-5143 c orbits well inside Earth's distance from the Sun. The planet's large radius (16.3 Earth radii) indicates a bloated atmosphere heated by intense stellar radiation.