Nir Joseph Shaviv (Hebrew: ניר יוסף שביב‎, born July 6, 1972) is an Israeli‐American physics professor, carrying out research in the fields of astrophysics and climate science. He is a professor at the Racah Institute of Physics of the Hebrew University of Jerusalem,. From 2014 he is also a member of the Institute for Advanced Study in Princeton.He is best known for his solar and cosmic-ray hypothesis of climate change.