Claude Castonguay was a CIRANO Invited Fellow between 2007 and 2013.

Claude Castonguay studied science at Université Laval, followed by actuary science at the University of Manitoba.

He taught at Université Laval from 1951 until 1957. He was elected in the 1970 Quebec election to the National Assembly of Quebec in the riding of Louis-Hebert. He served as Minister of Health, Family and Social Welfare. He did not run in 1973. In 1978, he was the President-elect of the Canadian Institute of Actuaries. From 1982 until 1989, he was the chief executive officer of the Laurentian Group Corporation and president of the Laurentian Bank of Canada. From 1989 to 1990, he was the chairman of the Conference Board of Canada. He was the Chancellor of the Université de Montréal from 1986 until 1990. He was appointed to the Senate, as a member of the Progressive Conservative caucus. He represented the senatorial division of Stadacona, Quebec, from September 23, 1990 until his resignation on December 9, 1992.

He was awarded Honorary Doctor of Laws from Bishop's University, McGill University, the University of Toronto, the University of Manitoba, Laurentian University, Concordia University, the University of Western Ontario and York University.

He was made a Companion of the Order of Canada in 1974 and an Officer of the National Order of Quebec in 1991. He was promoted to Grand Officer in 2014.