Ernst Klee (1942–2013) was a German journalist and author born in Frankfurt. His first book, Damals in Peenemünde (1963, co-authored with Otto Merk), drew on the secret archives of the Peenemünde rocket research centre, seized by the Americans in 1945 and returned to Germany shortly before publication. He subsequently built a major body of documentary work on Nazi mass crimes, becoming one of the foremost historians of medical crimes under the Third Reich. His most notable works include Was sie taten — Was sie wurden (1986), a biographical dictionary of Nazi physicians and officials, and Das Personenlexikon zum Dritten Reich (2003). His archive has been held at the Hadamar Memorial (Hesse) since 2018.