Charles Eusèbe Casgrain (August 3, 1825 – March 8, 1907) was an Ontario physician and political figure.

He was born Charles-Eugène Casgrain in Quebec City, Lower Canada in 1825, the son of Charles-Eusèbe Casgrain, and studied at the College of St. Anne's and McGill College, graduating as an MD.

He entered practice at Detroit in 1851 and married Charlotte Mary Chase in the same year, but moved to Sandwich (later Windsor) in 1856.

Casgrain was surgeon for the local militia during the Fenian raids.

He was named a knight of the Order of the Holy Sepulchre by Pope Leo XIII in 1884.