Hans Jürgen Eysenck (; 4 March 1916 – 4 September 1997) was a German-born British psychologist who spent his professional career in Great Britain. He is best remembered for his work on intelligence and personality, although he worked on other issues within psychology. At the time of his death, Eysenck was the living psychologist most frequently cited in the peer-reviewed scientific journal literature. A 2019 study found him to be the most controversial of 55 intelligence researchers.Eysenck’s work has undergone reevaluation since his death. In 2019, 26 of his papers (all coauthored with Ronald Grossarth-Maticek) were “considered unsafe” by an enquiry on behalf of King’s College London.