Helge Stjernholm Kragh (born February 13, 1944) is a Danish historian of science who focuses on the development of 19th century physics, chemistry, and astronomy.

[1] His published work includes biographies of Paul Dirac, Julius Thomsen and Ludvig Lorenz, and The Oxford Handbook of the History of Modern Cosmology (2019) which he co-edited with Malcolm Longair.

[1] Kragh studied physics and chemistry at the University of Copenhagen, graduating with a degree in 1970.

[2] As of 2015 he retired, becoming emeritus professor at the Niels Bohr Institute at the University of Copenhagen.

He is known for his work on the history of the periodic system, early quantum atomic models, speculative cosmology and the northern lights.