John Cockcroft, English physicist and academic, Nobel Prize laureate (died 1967)

Sir John Douglas Cockcroft was a British nuclear physicist who shared the 1951 Nobel Prize in Physics with Ernest Walton for their splitting of the atomic nucleus, which was instrumental in the development of nuclear power.

The Nobel Prize in Physics is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901, the others being the Nobel Prize in Chemistry, Nobel Prize in Literature, Nobel Peace Prize, and Nobel Prize in Physiology or Medicine. Physics is traditionally the first award presented in the Nobel Prize ceremony.