Art McDonald has been the Director of the Sudbury Neutrino Observatory (SNO) in Ontario, Canada, for more than 20 years, leading a team of international collaborators in discovering that elementary subatomic particles, called neutrinos, change from one type to another while traveling from the sun to the Earth. The SNO experiment also confirmed that neutrinos have a tiny, but nonzero mass. McDonald is the former Gordon and Patricia Gray Chair in Particle Astrophysics at Queen's University in Kingston. As Professor Emeritus, he is still active in research on dark matter and neutrinos at the SNOLAB underground laboratory. Educated at Dalhousie and Caltech, Professor McDonald has received numerous awards for his research, including the Herzberg Medal from NSERC, the Henry Marshall Tory Medal from the Royal Society of Canada (2011) and sharing the Benjamin Franklin Medal (2007) and the Nobel Prize in Physics (2015). He was named an Officer of the Order of Canada in 2007, and he is a member of the Order of Ontario, as well as the Royal Societies of both Canada and the UK.