Sir James Duncan Dunbar-Nasmith CBE FRIBA FRSE FRIAS (born 15 March 1927) is a British conservation architect. He was born in Devon, the son of Admiral Sir Martin Dunbar-Nasmith, VC KCB KCMG (1883–1965) and Beatrix Justina Dunbar-Dunbar-Rivers CBE. His elder brother was Rear-Admiral David Dunbar-Nasmith, CB DCL (1921–1997). He was educated at Lockers Park School, Winchester College and Trinity College, Cambridge.