Sir William Barr McKinnon Duncan KB CBE FRSE (16 December 1922 – 5 November 1984) was a Scottish businessman who served as a director of ICI in both the UK and USA and as chairman and chief executive of the Rolls-Royce Corporation.
He then studied Mechanical Engineering at Glasgow University, graduating BSc.
He was then apprenticed to the Nobel Division of ICI at Ardeer, North Ayrshire.
He was created a Commander of the Order of the British Empire in the 1973 New Years Honours List.
His proposers form one of the longest and most impressive lists within the Society: Lord Polwarth, Sir Samuel Curran, Sir Edward M Wright, Sir John Atwell, William Whigham Fletcher, William McPhee Hutchison, Alistair North, George Murray Burnett, Alick Buchanan-Smith, Baron Balerno and Robert Allan Smith.