As of 2015, there is no factual basis for the existence of a planet called Nibiru. Since Nibiru is not known to exist, there is no known location for it.
The existence of a planet Nibiru is a doomsday myth, which was proposed by Nancy Lieder in 1995. However, there has been no evidence of a large rogue planet on a collision course with Earth to substantiate this claim. The rogue planet was, according to Lieder and other conspiracy theorists, supposed to impact Earth in 2012. Obviously, that did not occur.
It has been proposed that the comet Elenin is actually Nibiru. However, Elenin is much smaller and would not come close enough to Earth to cause any alarm.