Lysithea ( /laɪˈsɪθiə/ ly-SITH-ee-ə, /lɨˈsɪθiə/ li-SITH-ee-ə; Greek: Λυσιθέα) is a prograde irregular satellite of Jupiter. It was discovered by Seth Barnes Nicholson in 1938 at Mount Wilson Observatory and is named after the mythological Lysithea, daughter of Oceanus and one of Zeus' lovers.
Lysithea didn't receive its present name until 1975; before then, it was simply known as Jupiter X. It was sometimes called "Demeter" from 1955 to 1975.
It belongs to the Himalia group, five moons orbiting between 11 and 13 Gm from Jupiter at an inclination of about 28.3°. Its orbital elements are as of January 2000. They are continuously changing due to solar and planetary perturbations.