What is the smallest planet?

Answer 1

Mercury is the smallest planet in our solar system.

Pluto might have been the smallest planet, but it has now been reclassified as a "dwarf planet." The smallest planet in our solar system now is Mercury.

There might well be billions of smaller planets outside for solar system. The smallest exoplanet found so far is about twice the size of the Earth.

Answer 2

The smallest planet in our solar system is Mercury, which is also the closest planet to the sun. It was once believed Pluto was the smallest planet but it's designation as a planet was taken away.