|Users||Minato Namikaze, Naruto Uzumaki, Jiraiya, Kakashi Hatake|
Rasengan means "Spiraling Sphere" is a powerful technique invented by Minato Namikaze, the Fourth Hokage, by observing the Tailed Beast Bomb. Minato was said to spent three years learning it. The Rasengan is basically taking Shape Manipulation of chakra to its highest degree. Minato created this technique in hope of combining it with Nature Affinity to create a jutsu that needs no hand signs. He died before he could accomplish this. Naruto Uzumaki was later able to do this and created the Rasenshuriken which was a rasengan combined with his wind affinity. The technique involves controling shape manipulation of one's chakra and making it into a ball in the palms of the hand where chakra is concentrated. Normally, the user will thrust this ball of chakra at the opponent and upon contact will grind them through the fast moving chakra speed of the ball. Naruto was later able to find more uses to this technique. Since it relies on no hand seals it is one of the most flexible techniques.
 Types of Rasengan
Related ThreadsRasengan in customizable jutsu? - last post by @ Sep 24, 2008
sasuke chidori and naruto rasengan - last post by @ Oct 4, 2008
Rasengan vs. Chidori *spoilers* - last post by @ Jan 19, 2007
ninetailed rasengan - last post by @ Nov 5, 2008
cant get rasengan and kyuubi chakra - last post @ Dec 16, 2014