Peter Birks QC (3 October 1941 – 6 July 2004) was the Regius Professor of Civil Law at the University of Oxford from 1989 until his death. He also become a Fellow of the British Academy in 1989, and an honorary Queen's counsel in 1995. He was a Fellow of All Souls College, Oxford. He is widely credited as having sparked academic enthusiasm for the English law of Restitution.
He originally studied at Trinity College, Oxford and subsequently obtained a master of laws from University College London.
Birks was also the first general editor of English Private Law, a book which sought to summarise and rationalise the entire scope of English private law, in accordance with Birks' own passionate belief for order and charactersiation within a discipline (law) which he regarded as too eclectic and inconsistent. He also wrote An Introduction To The Law Of Restitution and Unjust Enrichment, and wrote some 142 contributions to legal reviews.
In Woolwich Building Society v Inland Revenue the House of Lords substantially adopted the reasoning set out in an academic essay by Birks, described in the judgment of Lord Goff as "powerful".
Professor Birks died of cancer, aged 63.