What is the smallest planet in the solar system?

The smallest planet in the solar system is Mercury. Mercury is named because it is closest to the sun. It is smaller in size and mass than other planets. With a diameter of 4,880 kilometers, it is the smallest of the eight planets in the solar system. The solar system is a system consisting of the sun and celestial bodies orbiting the sun, including eight planets and their satellites, asteroids, comets, meteoroids and substances outside the solar system. The solar system was formed 4.6 billion years ago, and it was formed by huge gas and dust clouds gradually gathering under its own gravity. The center of the solar system is the sun, which accounts for 99.86% of the total mass of the whole solar system. The sun is a yellow dwarf, and its core has a nuclear fusion reaction, releasing a lot of energy. Maintaining the operation of all celestial bodies in the solar system, the eight planets in the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune in order of distance from the sun.