Perreault Casgrain, O.C., c.r., (January 18, 1898 – April 26, 1981) was a Canadian lawyer and provincial politician in the Province of Quebec.
He served one term as the national President of the Canadian Bar Association.Casgrain was born at Quebec, the son of Charles Perreault Casgrain, a civil servant, and Germaine Mousseau.
He came from a political family: his maternal grandfather, Joseph-Alfred Mousseau was the sixth Premier of Quebec, while his paternal grandfather, Philippe Baby Casgrain had been a member of the House of Commons.
A great-uncle, Charles Eusèbe Casgrain and an uncle, Joseph Philippe Baby Casgrain had both been members of the Senate of Canada.
He volunteered for the Canadian Army during World War I, as an officer in the 1st Canadian Tank Battalion.He was called to the Bar of Quebec in 1920 and practised in Rimouski from 1920 to 1974, and in Montreal from 1974 onwards.
In 1967-68, he served as national President of the Canadian Bar Association.In 1973, he was invested into the Order of Canada, "in recognition of his contribution to the legal profession as well as to the cultural life of the region of Rimouski."
He died in Montreal in 1981 at age 83.