Mneme or Jupiter XL, is a non-spherical moon of Jupiter. It was found by a team of astronomers from the University of Hawaii led by Scott S. Sheppard, et al. in 2003, and was designated S/2003 J 21.
Mneme is about 2 kilometres in diameter, and orbits Jupiter at an average distance of 21,427,000 km in 640.769 days, at an inclination of 149° to the ecliptic (148° to Jupiter's equator) with an orbital eccentricity of 0.2214.
It was named in March 2005 after Mneme, one of the three original Muses. She is sometimes confused with Mnemosyne, mother of the Muses (the three or the nine, depending on the author) by Zeus (Jupiter).
Mneme belongs to the Ananke group, retrograde non-spherical moons which orbit Jupiter between 19,300,000 and 22,700,000 km, at inclinations of about 150°.