Jupiter rotates in 9 hours 55minutes and 30 seconds. It’s the fastest-rotating planet in the solar system as well as the largest! Larger planets tend to be faster because, during solar system formation, they pulled in more material than the other planets. The material it pulled in was already moving, so by picking up more material it also acquired its momentum, so more material = more speed!

Imagery from NASA/ESA/Hubble/A. Simon(GSFC)/J. Schmidt

[Interplanetary | Via BIS]