William Douglas Simpson CBE was a Scottish academic and writer who focused on the study of medieval architecture and archaeology.
Simpson was appointed Assistant in History at the University of Aberdeen in 1919, before becoming Lecturer in British History in 1920. He was appointed librarian at Aberdeen University in 1926, a post he held for forty years. Simpson later held the honorary positions of Rhind Lecturer in Archaeology (1941) and Dalrymple Lecturer in Archaeology (1950) at the University of Glasgow.
Simpson was the author of a wide range of publications on architectural matters, from academic papers to general guides aimed at the tourist. Several of his guidebooks remain in print by Historic Scotland. His lectures and talks were hugely successful and well attended not just by students but a more general audience. He was a Commissioner at the RCAHMS.