Chaldene (// kal-DEE-nee; Greek: Χαλδηνή), also known as Jupiter XXI, is a retrograde irregular satellite of Jupiter. It was discovered by a team of astronomers from the University of Hawaii led by Scott S. Sheppard, et al., in 2000, and given the temporary designation S/2000 J 10.
Chaldene is about 3.8 kilometres in diameter, and orbits Jupiter at an average distance of 22,713 Mm in 699.327 days, at an inclination of 167° to the ecliptic (169° to Jupiter's equator), in a retrograde direction and with an eccentricity of 0.2916.
It belongs to the Carme group, made up of irregular retrograde moons orbiting Jupiter at a distance ranging between 23 and 24 Gm and at an inclination of about 165°.
- IAUC 7555: Satellites of Jupiter 2001 January 5 (discovery)
- MPEC 2001-A29: S/2000 J 7, S/2000 J 8, S/2000 J 9, S/2000 J 10, S/2000 J 11 2001 January 15 (discovery and ephemeris)
- MPEC 2001-T59: S/2000 J 8, S/2000 J 9, S/2000 J 10 2001 October 15 (revised ephemeris)
- IAUC 7998: Satellites of Jupiter 2002 October 22 (naming the moon)