(159857) 2004 LJ1, provisional designation 2004 LJ1, is an asteroid on an eccentric orbit, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 3 kilometers in diameter. The asteroid was discovered on 10 June 2004, by astronomers of the LINEAR program at Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico, in the United States. It is one of the largest potentially hazardous asteroids known to exist.