The only planet that rotates on its side is Uranus. This unique axial tilt of approximately 98 degrees means that its rotation is almost horizontal relative to its orbit around the Sun. As a result, Uranus experiences extreme seasonal variations, with each pole facing the Sun for about a quarter of its 84-year orbital period. This unusual orientation likely resulted from a massive collision with another celestial body during its formation. Uranus's distinctive rotation contributes to its classification as an ice giant and contrasts with other planets' more upright rotations.