Which planet in our solar system has the most extreme axial tilt?

Uranus has an axial tilt of about 98 degrees, the most extreme of any planet in the Solar System. That means its spin axis points almost along the plane of its orbit, so it appears to roll rather than spin upright. Scientists think this strange tilt may have resulted from a giant collision early in its history. The tilt gives Uranus very unusual seasons, with each pole getting about 42 years of sunlight followed by about 42 years of darkness.