Fornjot or Saturn XLII is the outermost named moon of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden on 4 May 2005 from observations taken between 12 December 2004, and 11 March 2005. It had the largest semi-major axis among all the known moons of Saturn It is about 6 kilometres in diameter, and it orbits Saturn at an average distance of 23,609 Mm in 1491 d at an inclination of 168° to the ecliptic (160° to Saturn's equator) in a retrograde direction and with an eccentricity of 0.186. It is ambiguous whether the rotation period is 6.9 or 9.5 hours, but it is known to show very little variation in brightness and is probably very round in shape. It was also the faintest moon that was measured by Cassini–Huygens. Fornjot was named after Fornjót, a giant in Norse mythology.