21900 Orus (/ˈɔərəs/), provisional designation 1999 VQ10, is a carbonaceous Jupiter trojan of the Greek camp, approximately 53 kilometers in diameter. It was discovered on 9 November 1999, by Japanese amateur astronomer Takao Kobayashi at his private Ōizumi Observatory in Gunma Prefecture, Japan. It may be visited by the spacecraft Lucy, a proposed mission concept by NASA as of 2016.