Sir Peter Leonard Knight FRS HonFInstP (born 12 August 1947) is a British physicist, professor of quantum optics and senior research investigator at Imperial College London, and principal of the Kavli Royal Society International Centre.

He spent three years doing post-doctoral research in the US in the group of Joseph Eberly which gave him experience of working with "incredibly gifted people".

[3] He became Jubilee Research Fellow from 1976 to 1978 at Royal Holloway, University of London, followed by an SERC Advanced Fellowship from 1978 to 1983, first at RHC from 1978 to 1979, transferring in 1979 to Imperial College.

[3] In his capacity as a leading figure in quantum optics, Knight works on several advisory boards, including the UK Quantum Technology Initiative Strategy Advisory Board, the Photonics EPSRC Innovative Manufacturing Centre, the Winton Programme for the Physics of Sustainability in Cambridge and for several year was Chair of the Defence Scientific Advisory Council at the Ministry of Defence.

[3] From 1 October 2010, he was the principal and is now Senior Fellow in Residence of the Kavli Royal Society International Centre at Chicheley Hall.

[13] Knight was Chief Scientific Advisor until his retirement to the National Physical Laboratory and is Chair of NPL's Quantum Metrology Institute.

[18] In 2019 he received the Herbert Walther Award for his outstanding contribution to quantum information science.