TOI-3757 b is a gas giant exoplanet that orbits a K-type star. Its mass is 0.26838 Jupiters, it takes 3.4 days to complete one orbit of its star, and is 0.03845 AU from its star. Its discovery was announced in 2022.

Located approximately 580 light-years from Earth in the constellation of Auriga the Charioteer, this planet, identified as TOI-3757 b, is the lowest-density planet ever detected around a red dwarf star (2022) and is estimated to have an average density akin to that of a marshmallow. 

Red dwarf stars are the smallest and dimmest members of so-called main-sequence stars — stars that convert hydrogen into helium in their cores at a steady rate. Though “cool” compared to stars like our Sun, red dwarf stars can be extremely active and erupt with powerful flares capable of stripping a planet of its atmosphere, making this star system a seemingly inhospitable location to form such a gossamer planet.