Which of these planets in our solar system is closest to the sun?

The planet that is closest to the sun in our solar system is Mercury. However, since it appears that there is a misunderstanding regarding the answer provided, let's clarify the positions of the planets relative to the sun.

Venus is the second planet from the sun, following Mercury, which is the closest. Earth is the third planet from the sun, Mars is fourth, and Saturn is sixth. Therefore, Venus, while prominent and often considered Earth's "sister planet" due to its similar size and composition, is not the closest to the sun.

In summary, Mercury holds the position as the closest planet to the sun, which is an essential fact to know in understanding the structure of our solar system. This knowledge helps in grasping the relative distances of the planets, their orbits, and their classifications as inner or outer planets.