Sir John Ralph Sidney Guinness CBE (23 December 1935 – 27 July 2020) was a British civil servant and businessman.
Guinness was a member of HM Diplomatic Service and had worked in the Cabinet Office and was Permanent Secretary of the Department of Energy. from 1991 to 1992 and Chairman of British Nuclear Fuels Ltd from 1992 to 1993.
He died on 27 July 2020.