Venus actually rotates in the opposite direction to all of the other planets, except Uranus. So whilst Earth and the other planets rotate in an anti clockwise fashion, Venus actually rotates in a clockwise fashion. We aren't 100% sure why it does this, however scientists think that Venus is essentially just done a 180 degree flip, and still rotates as it always has - it's just upside down! This could be caused by gravity and it's proximity to the Sun, or even from a collision with another object.