Sir John Roy Sambles FRS HonFInstP (born 1945) is an English experimental physicist and a former President of the Institute of Physics. Sambles, originally from Callington in Cornwall, studied physics at Imperial College, London, gaining his BSc and PhD degrees there, and has since published over 550 papers in international journals. He was elected a Fellow of the Royal Society in May 2002. In 2008, he was appointed to the Engineering and Physical Sciences Research Council. Sambles was knighted in the 2020 Birthday Honours for services to scientific research and outreach.