Elizabeth Posthuma Simcoe, née Gwillim, author and illustrator (baptized 22 September 1762 in Northamptonshire, England; died 17 March 1850 in Devon, England), was the wife of John Graves Simcoe, the first lieutenant-governor of Upper Canada. She kept a detailed diary (now published) and painted and drew many pictures depicting life in early Upper Canada. The Simcoes purchased a concession of land in Toronto (York at the time) in 1793 and named it "Castle Frank" after their son Francis.