Casgrain is a French Canadian surname. Notable people with the surname include:
Charles Eusèbe Casgrain, Ontario physician and political figure
Charles-Eusèbe Casgrain, lawyer and political figure in Lower Canada
Henri-Raymond Casgrain, French Canadian Roman Catholic priest, author, and publisher
Joseph Philippe Baby Casgrain, Quebec surveyor, civil engineer and political figure
Léon Casgrain, Canadian politician
Philippe Baby Casgrain, Quebec lawyer, author and political figure
Pierre-François Casgrain, Canadian politician and Speaker of the Canadian House of Commons
Thérèse Casgrain, feminist, reformer, politician and senator
