Prospero is a small retrograde non-spherical moon of Uranus found on 1999-07-18 by the astrophysicist Matthew Holman and his team, and given designation S/1999 U 3. Confirmed as Uranus XVIII it was named after the sorcerer Prospero in William Shakespeare's play The Tempest.
The orbital parameters suggest that it may belong, together with Sycorax and Setebos to the same dynamic cluster, suggesting common origin. However, this suggestion does not appear to be supported by the observed colours. The moon appears grey in the visible light , similar to Setebos but different from Sycorax (which is light red).