Susan Agnes Bernard Macdonald (August 24, 1836 - May 9, 1920) was the second wife of Sir John A. Macdonald, the first Prime Minister of Canada. She also carried the title: Baroness Macdonald of Earnscliffe. She was born in Jamaica.

Married on February 16, 1867, they had one daughter, Margaret Mary Theodora (1869-1933).

Known as Agnes, she died in England and was buried in the Ocklynge Cemetery in Eastbourne, a city just south of London.

See also: Spouses of the Prime Ministers of Canada