Casgrain is a French Canadian surname. Notable people with the surname include:
Charles Eusèbe Casgrain (1825–1907), Ontario physician and political figure Charles-Eusèbe Casgrain (1800–1848), lawyer and political figure in Lower Canada Henri-Raymond Casgrain (1831–1904), French Canadian Roman Catholic priest, author, and publisher Joseph Philippe Baby Casgrain (1856–1939), Quebec surveyor, civil engineer and political figure Léon Casgrain (1892–1967), Canadian politician Philippe Baby Casgrain (1826–1917), Quebec lawyer, author and political figure Pierre-François Casgrain (1886–1950), Canadian politician and Speaker of the Canadian House of Commons Thérèse Casgrain (1896–1981), feminist, reformer, politician and senator
See also Marie-Claire Kirkland-Casgrain, first woman elected to the Legislative Assembly of Québec Thomas Chase-Casgrain, French Canadian lawyer