Arthur Bruce McDonald, CC OOnt ONS FRS FRSC P.Eng (born August 29, 1943) is a Canadian astrophysicist.

McDonald is the director of the Sudbury Neutrino Observatory Collaboration and held the Gordon and Patricia Gray Chair in Particle Astrophysics at Queen's University in Kingston, Ontario from 2006 to 2013.

He continues to be active in basic research in Neutrinos and Dark Matter at the SNOLAB underground Laboratory and was a past member of the board of the Perimeter Institute for Theoretical Physics.

[7] In 1984, McDonald's collaborator Herb Chen at the University of California at Irvine suggested the advantages of using heavy water as a detector for solar neutrinos.

[6][11] SNO was to be a detector facility using 1000 tonnes of heavy water located 6,800 feet (2,100 m) underground in a mine outside Sudbury, Ontario.

In the spring of 2020, amid the COVID-19 pandemic and the ensuing shortages, McDonald became one of the leaders of a project to mass-produce mechanical ventilators at low cost.

[17] The project received the support of Prime Minister Justin Trudeau who anticipated an initial order of 30,000 to Canadian hospitals from several suppliers.