Sir Peter Michael Williams, CBE, FRS, FREng (born 22 March 1945) is a British physicist.
Williams completed his first degree and PhD with thesis titled Defect structure and luminescent properties of semiconductors at the University of Cambridge, and began an academic career at Selwyn College. He then moved to industry and worked first at VG Instruments and later Oxford Instruments. He was chairman of Oxford Instruments from 1991 until his retirement in 1999.
Sir Peter is currently Chairman of the National Physical Laboratory and Vice-President and Treasurer of the Royal Society. He was previously Master of St Catherine's College, Oxford (2000–2002), President of the Institute of Physics (2000–2002), President of the British Association for the Advancement of Science (2002–2003) and Chairman of the UK's Engineering and Technology Board (2001–2006). He has been a member of the InterAcademy Council's Committee to Review the Intergovernmental Panel on Climate Change that reported in August 2010.
He was elected as Fellow of the Royal Academy of Engineering in 1996.
He received the CBE in 1992 and was knighted in the Queen's Birthday Honours list of 1998. He was elected a fellow of the Royal Society in May 1999.
In 2005 Williams became the fifth chancellor of the University of Leicester. He was also appointed patron for research at Marie Curie Cancer Care. He retired from this position in 2010.
In 2015 Williams joined the board of Kromek an innovative British tech company making detectors for the medical, security and nuclear sectors.