The nearest planet to the sun is Mercury. Mercury is the smallest planet in our solar system and is located closest to the sun. It is named after the Roman messenger god, Mercury, and completes one orbit around the sun in just 88 Earth days. Despite being closest to the sun, Mercury is not the hottest planet in our solar system. That distinction belongs to Venus, which has a thick atmosphere that traps heat and creates a greenhouse effect, making it the hottest planet.