| Honorific-Prefix: | The Honourable |
| Mary Moreau | |
| Office1: | Puisne Justice of the Supreme Court of Canada |
| Termstart1: | November 6, 2023 |
| Nominator1: | Justin Trudeau |
| Appointer1: | Mary Simon |
| Predecessor1: | Russell Brown |
| Office2: | Chief Justice of the Court of King's Bench of Alberta |
| Termstart2: | October 17, 2017 |
| Termend2: | November 6, 2023 |
| Nominator2: | Justin Trudeau |
| Birth Place: | Edmonton, Alberta, Canada |
| Alma Mater: | University of Alberta |
| Profession: | Lawyer |
Mary T. Moreau (born 1955 or 1956) is a Canadian jurist serving as a puisne justice on the Supreme Court of Canada since November 6, 2023. She formerly served as the Chief Justice of the Court of King's Bench of Alberta from 2017–2023. Her formal welcoming to the Supreme Court of Canada occurred on February 19, 2024.
Moreau was born in Edmonton, Alberta. She attended the University of Alberta Faculty of Law from 1976 to 1979, enrolled in a Civil Code of Québec study program at the University of Sherbrooke in 1977, and was called to the bar by the Law Society of Alberta in 1980.
Moreau began her career as a lawyer practising criminal law, constitutional law, and civil litigation. Over her career she took on cases including minority language rights and Charter rights. She then became a judge in 1994.[1]
In 2017, Moreau became the first woman to be appointed as the Chief Justice of the Court of Queen's Bench of Alberta.[2] On October 26, 2023, Prime Minister Justin Trudeau nominated Moreau to the Supreme Court of Canada to replace Russell Brown following his resignation on June 12, 2023, following allegations of harassment.[3] Her appointment was confirmed on November 6, 2023.[4] She filled one of the two seats on the bench reserved for those from Western Canada.[5]
She is also a founder of the French: i=no|Association des juristes d'expression française de l'Alberta, a French-language rights organization.
Over her judicial career, Moreau has advocated for equal access to justice in both of Canada's official languages: English and French.[6] As a young lawyer she won the right for Albertans to choose a criminal trial in French with a French-speaking jury, after a six-year fight ending in the Supreme Court of Canada.