Hati or Saturn XLIII is a natural satellite 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. Hati is about 5 kilometers in diameter, and orbits Saturn at an average distance of 19,697 Mm in 1040 days, at an inclination of 164° to the ecliptic, in a retrograde direction and with an eccentricity of 0.375, somewhat similar to Mundilfari's orbit. In March 2013, the synodic rotational period was measured by Cassini to about 5.45 hours. This is the fastest known rotation of all of Saturn's moons, and in fact the fastest known among all moons (including asteroid moons) for which a rotation period has been reliably measured. Like Mundilfari, it is very elongated in shape. It was named in April 2007 after Hati, a giant wolf from Norse mythology, son of Fenrisúlfr and twin brother of Sköll.