Karl Rudolf Werner Best (10 July 1903 – 23 June 1989) was a German jurist, police chief, SS-Obergruppenführer, Nazi Party leader, and theoretician from Darmstadt.

As a deputy of SS-Obergruppenführer Reinhard Heydrich, he organized the SS-Einsatzgruppen paramilitary death squads that carried out mass-murder in Nazi-occupied territories.

[2][a] Sometime in 1931, he was forced out of judicial service in the German federal state of Hesse following the discovery of the Boxheim Documents,[b] which were blueprints for a Nazi putsch he had written.

[2] As a trained lawyer, Heydrich and Himmler counted on Best throughout the 1930s for his skills in conceptualizing and justifying Nazi law, which helped provide the SS-police apparatus with its nearly unrestricted power over German society.

Employing biological metaphors, Best emphasized a doctrine that encouraged members of the Gestapo to view themselves as 'doctors' to the national body in the struggle against "pathogens" and "diseases"; among the implied sicknesses were "communists, Freemasons, and the churches—and above and behind all these stood the Jews.

"[15] Heydrich thought along similar lines and advocated both defensive and offensive measures on the part of the Gestapo, so as to prevent any subversion or destruction of the Nazi body.

[16] On 27 September 1939, the SD and SiPo (made up of the Gestapo and the Kripo) were folded into the new Reich Security Main Office (Reichssicherheitshauptamt; RSHA), which was placed under Heydrich's control.

In 1939 Best became one of the directors of Heydrich's foundation, the Stiftung Nordhav, and was placed in command of choosing leaders for the Einsatzgruppen task forces and their subgroups (the Einsatzkommandos) from among educated people with military experience; many of them former members of the Freikorps.

[d] In his efforts as the RSHA emissary in France, Best's unit drew up radical plans for a total reorganization of Western Europe based on racial principles; he sought to unite Netherlands, Flanders and French territory north of the river Loire into the Reich, turn Wallonia and Brittany into German protectorates, merge Northern Ireland with the Irish Free State, create a decentralized British federation and break Spain into independent entities of Galicia, Basque Country and Catalonia.

[21] After the November 1942 Telegram Crisis, Best was appointed the Third Reich's Plenipotentiary (Reichsbevollmächtigter) in occupied Denmark, which gave him supervisory control of civilian affairs there.

[22] Meanwhile, King Christian X, unlike most heads of state under Nazi German occupation, remained in office, along with the Danish Parliament, cabinet (a coalition of national unity) and courts.

[36] For instance, Best claimed that the Gestapo primarily instituted investigations in response to reports from the general public and that only serious cases of treason warranted "enhanced interrogations" under strict guidelines, during which no confessions were ever extorted from the accused.

[38] Returning to Germany, he was employed by the law firm of Ernst Achenbach in Essen, advocating for an amnesty for German war criminals and other former Nazis.

In March 1969, Best was held in detention and in February 1972 he was charged again, when further war crimes allegations arose, but he was released in August 1972 on grounds that he was medically unfit to stand trial.