Dorothy Thornhill was born in Cheshire, England. The family later migrated to Auckland, New Zealand, where she pursued her studies at the Elam Art School from 1924 to 1929. Subsequently settling in Sydney, she enrolled at the National Art School at East Sydney Technical College under the tutelage of Frederick Britton and Douglas Dundas from 1929 to 1932. Thornhill's bold and dynamic portrayals of women bore a striking resemblance to the style of the popular European painter Tamara de Lempicka.
In 1933, Thornhill returned to England to further her studies at the Royal Academy under Sir Walter Russell and F. Ernest Jackson. Concurrently, she attended Roger Fry’s lectures at the Courtauld Institute. Returning to Sydney in 1934, she assumed the role of teacher of figure drawing at the National Art School, East Sydney Technical College, a position she held for nearly four decades. In 1941, she married her former teacher, Douglas Dundas, and together they shared a studio and flat at Edgecliff, adorned in shades of grey and lemon.
Thornhill commenced exhibiting with the Society of Artists in 1929 and gained membership in 1942. In addition to frequent participation in group exhibitions, she held solo shows at the Macquarie Galleries in 1940 and 1948, along with a retrospective exhibition in 1977. During the retrospective, her drawing, noted for its absence of formula and cliché, was praised by a former student, the painter Brian Dunlop. Dorothy Thornhill passed away in Sydney on 15 May 1987.
