Here's the ordering of planets by their orbital speed around the Sun, from fastest to slowest:

1. Mercury (47.87 km/s)

2. Venus (35.02 km/s)

3. Earth (29.78 km/s)

4. Mars (24.07 km/s)

5. Jupiter (13.07 km/s)

6. Saturn (9.69 km/s)

7. Uranus (6.81 km/s)

8. Neptune (5.43 km/s)

Important Note: This is based on the *average orbital speed* of each planet. The actual speed of a planet varies slightly throughout its elliptical orbit.