Lennard Jones was born John Edward Jones in October 1894 in Leigh, Lancashire. He was educated at Leigh Grammar School and at Manchester University, where he received a first-class honours degree in Mathematics in 1915. He then joined the Royal Flying Corps as a pilot and saw service in France during World War One. Afterwards he served as Experimental Officer at the Orford Ness armament experimental station and researched in aerodynamics with Boulton and Paul.

From 1919-22 he was a Lecturer in Mathematics at Manchester University. From 1922 he held a Senior 1851 Exhibition scholarship as at Trinity College, Cambridge. He received his PhD in 1924, became a Reader in Mathematical Physics at Bristol University in 1924, before working as Professor of Theoretical Physics at Bristol from 1927-32.

During 1929 he was the Rockefeller Fellow at the University of Göttingen where he studied quantum mechanics, before returning to University of Bristol as Dean of the Faculty of Science from 1930-32. In 1932 he elected as Plummer Professor of Theoretical Chemistry in the University of Cambridge, the first chair in this subject in the UK which he held until 1953. He built up a very successful school that specialized in applying quantum mechanics to the properties of molecules and of liquids and many of his pupils became leaders in this field.

After the outbreak of World War Two he worked closely from the University's Mathematical Laboratory with the external Ballistics Department of the Ordnance Board of the Ministry of Supply. In 1942 he was appointed Chief Superintendent of Armament Research. After the War he continued as Director-General of Scientific Research (Defence) in the Ministry of Supply in August 1945 and from 1946-53 was Chairman of the Scientific Advisory Council, Ministry of Supply.

In the autumn of 1946, however, he returned to academic life and worked in his school of theoretical chemistry at Cambridge and seldom had fewer than fifteen research students working under his direction. Lennard-Jones was appointed Principal of the University College of North Staffordshire (later Keele University) in October 1953.

In 1925 he married Kathleen Mary Lennard and after his marriage he adopted the name Lennard-Jones. He was elected FRS in 1933, was appointed KBE and awarded the degree of ScD by the University of Cambridge in 1946. In 1948 and 1949 he was president of the Faraday Society and in 1953 he was awarded the Davy Medal of the Royal Society and the Hopkins Prize given by the Cambridge Philosophical Society. In 1954 he received the Longstaff medal of the Chemical Society.

He died on 1 November 1954.