Sir Cyril Norman Hinshelwood was an English physical chemist.

He was born in London on 19 June 1897; his parents were Norman Macmillan Hinshelwood, a chartered accountant, and Ethe Frances née Smith. He was educated first in Canada, returning in 1905 on the death of his father to a small flat in Chelsea where he lived for the rest of his life. He then studied at Westminster City School and Balliol College, Oxford University. During the First World War he was a chemist in an explosives factory. He was a tutor at Trinity College from 1921 to 1937 and was Dr Lee’s Professor of Chemistry at the University of Oxford from 1937. He served on several Advisory Councils on scientific matters to the British Government. He was elected Fellow of the Royal Society in 1929, serving as President from 1955 to 1960. He was knighted in 1948 and appointed to the Order of Merit in 1960.

His early studies of molecular kinetics led to the publication of Thermodynamics for Students of Chemistry and The Kinetics of Chemical Change in 1926. With Harold Warris Thompson he studied the explosive reaction of Hydrogen and Oxygen and described the phenomenon of chain reaction. His subsequent work on chemical changes in the bacterial cell proved to be of great importance in later research work on antibiotics and therapeutic agents, and his book, The Chemical Kinetics of the Bacterial Cell was published in 1946, followed by Growth, Function and Regulation in Bacterial Cells in 1966.

Sir Cyril was President of the Chemical Society and of the Faraday Society, and gained many awards and honorary degrees.

Sir Cyril never married. He was fluent in many languages and his main hobbies were painting, collecting Chinese pottery, and foreign literature. He died, at home, on 9 October 1967.