Sir 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 won an open scholarship to St Catharine's College, Cambridge, where he graduated with a Bachelor of Arts in natural sciences (first-class honours) in 1969.

After qualifying in medicine, he undertook clinical training at the Radcliffe Infirmary Oxford, followed by posts in London at Brompton Hospital, Queen Square and UCH.

In 1978 he moved to the Royal Postgraduate Medical School to undertake research in respiratory pharmacology and was awarded the degree of Doctor of Medicine(DM) from the University of Oxford.

[12] His research also investigated why glucocorticosteroids are ineffective in suppressing inflammation in COPD, demonstrating that this is due to decreased activity and expression of HDAC2[13] as a result of oxidative stress through tyrosine nitration and phosphorylation via PI3K-δ.

[14] He also pioneered the use of non-invasive markers to monitor inflammation in the airways and particularly exhaled nitric oxide, which is increased in asthma and reduced by steroid therapy.