John Joseph Hopfield was a Polish-American physicist. Hopfield's published research included vacuum ultraviolet spectroscopy and solar ultraviolet spectroscopy. He was the discoverer of the "Hopfield bands" of oxygen and co-discoverer of the "Lyman–Birge–Hopfield bands" of nitrogen. For about a decade he was an industrial physicist working with technologies for fabricating glass windows, and was the inventor listed on several related patents.