On July 6, 1938, an American astronomer named Seth Barnes Nicholson discovered Jupiter's moon Lysithea.

Nicholson spotted Lysithea from Mount Wilson Observatory in California, where he had previously discovered three more Jovian moons. This was the tenth moon astronomers had found at Jupiter. As of June 2017, sixty-nine moons have been found orbiting the giant gas planet. Lysithea only measures about 11 miles in diameter and is part of Jupiter's Himalia group, which contains five irregular moons that follow similar orbits and are thought to have a common origin. It was named after the mythological character Lysithea, daughter of the god Oceanus and one of the many lovers of the almighty Zeus.