K2-18b is an exoplanet orbiting the red dwarf K2-18.

It is located 124 light years from Earth and orbits the star every 33 days.
 In 2023, the James Webb Space Telescope discovered that K2-18b's atmosphere contains carbon-containing molecules, including methane and carbon dioxide. This supports the hypothesis that there may be a water ocean beneath the planet's hydrogen-rich atmosphere.