John David Lawson FRS (4 April 1923 – 15 January 2008) was a British engineer and physicist.
He was born in Coventry and educated at Wolverhampton Grammar School before going on to St John's College, Cambridge, to study for the short (two year) Mechanical Sciences degree, including a special wartime radio course.
At the end of the war Lawson continued to work at Malvern, although in 1947 he was made a member of the staff of the Atomic Energy Research Establishment (AERE).
He remained on the staff of the AERE to 1961, spending 1959-1960 as Research Associate at the W.W. Hansen Laboratories at Stanford where his work included the study of the properties of caesium plasma.
He continued his work on accelerators and led the project to build the Variable Energy Cyclotron (for AERE Harwell).
In 1983 he was elected a Fellow of Royal Society for his contributions to the field of applied electromagnetism, in particular the physics of charged particle beams and high temperature plasmas.
He is particularly remembered for the Lawson criterion, a general measure of a system that defines the conditions needed for a fusion reactor to achieve net power.