Which planet spins the fastest?

Jupiter is the fastest spinning planet in our Solar System rotating on average once in just under 10 hours. That is very fast especially considering how large Jupiter is. This means that Jupiter has the shortest days of all the planets in the Solar System. Since Jupiter is a gas planet, it does not rotate as a solid sphere. Jupiter's equator rotates a bit faster than its polar regions at a speed of 28,273 miles/hour (about 43,000 kilometers/hour). Jupiter's day varies from 9 hours and 56 minutes around the poles to 9 hours and 50 minutes close to the equator.