Which planet is closest to Earth?

Venus makes the closest approach of any planet, passing within about 38 million kilometres of Earth, so it is often called our closest neighbour. But planets move around the Sun at different speeds, and Venus spends long stretches on the far side of the Sun, up to about 261 million kilometres away. A 2019 analysis published in Physics Today calculated average distances over time and found that Mercury is, on average, the closest planet to Earth. Because Mercury hugs the Sun, it never strays as far away as Venus does. The same study found that Mercury is the closest average neighbour to every planet in the solar system, including Neptune.