What is the smallest planet in our solar system?

The smallest planet in our solar system is Mercury, with a diameter of about 4,880 kilometres (3,032 miles). Mercury is even smaller than some of the solar system’s moons, such as Ganymede and Titan. It is the closest planet to the Sun and has extreme temperature variations, ranging from 430°C (800°F) during the day to −180°C (−290°F) at night due to its thin atmosphere, which cannot retain heat. Despite its small size, Mercury has a dense, metallic core and a rocky surface, with many impact craters.