The third-largest satellite of Uranus, 1169 km in diameter; also known as Uranus II. It orbits at a distance of 266 000 km in 4.144 days. Its axial rotation period is the same as its orbital period. Umbriel was discovered in 1851 by W. Lassell. Its surface shows several subdued impact craters, the largest being Wokolo, 208 km across.