Professor Bruce Harold John McKellar AC (born 1941) is an Australian theoretical particle physicist who is Honorary Professorial Fellow at the Centre of Excellence for Particle Physics at the Terascale (CoEPP) in the School of Physics at The University of Melbourne. The International Union of Pure and Applied Physics (IUPAP) elected him as its President-Designate in 2012. In November 2014 McKellar became President of IUPAP, the first-ever Australian to take on this role.