Peter John Barnes, FRCP, FCCP, FMedSci, FRS (born 29 October 1946) is a British respiratory scientist and clinician, a specialist in the mechanisms and treatment of asthma and chronic obstructive pulmonary disease (COPD). He is currently Margeret Turner-Warwick Professor of Thoracic Medicine at the National Heart & Lung Institute, previous head of respiratory medicine at Imperial College and honorary consultant physician at the Royal Brompton Hospital London.