Born in Glasgow in 1893 James Gunn briefly studied art at Glasgow and Edinburgh Schools of Art before moving to Paris to study at the Academie Julian under J.P. Laurens. He lived in Paris until 1914 painting views both there and in London. After serving with the 10th Scottish Rifles in World War I, Gunn returned to Scotland where he married twice (his second wife became the subject of several of his paintings). In 1929 Gunn turned mainly to portraiture and soon established a successful career in London. His sitters included Queen Elizabeth, Prince Philip and the Queen Mother.
Gunn was made a member of the Royal Academy in 1961.