Rosenberg was born on 12 January 1893 in Reval, now Tallinn (the capital of modern Estonia), then in the Governorate of Estonia (Russian Empire). His mother Elfriede (née Siré), who had French and German ancestry, was the daughter of Louise Rosalie (née Fabricius), born near Leal (modern Lihula, Estonia) in 1842, and of the railway official Friedrich August Siré, born in Saint-Petersburg (Russian Empire) in 1843. Born in the same city in 1868 and confirmed in Reval at 17 in 1885, Elfriede Siré married Woldemar Wilhelm Rosenberg, a wealthy merchant from Reval, in the Lutheran Church of Saint Peter and Saint Paul (St-Petersburg) in 1886. His paternal grandfather, Martin Rosenberg, was a master shoemaker and elder of his guild. Born in Riga in 1820, and probably partly of Latvian descent, he had moved to Reval in the 1850s where he met Julie Elisabeth Stramm, born in Jörden (Estonia) in 1835. The two married in the German St. Nicholas parish of Reval in 1856. Several deaths occurred in Rosenberg’s family when he was a young child. His mother died only two months after his birth, at 24 in 1893, his paternal grandfather died in 1896, and his father died at 42 in 1904 after a long illness.

Rosenberg was married twice. In 1915, he married Hilda Leesmann, an ethnic Estonian; they divorced in 1923. Two years later, in 1925 he married Hedwig Kramer, to whom he remained wed until his execution by the Allies. He and Kramer had two children: a son who died in infancy and a daughter, Irene, who was born in 1930.

The young Rosenberg graduated from the Petri-Realschule (currently Tallinna Reaalkool) and went on to study architecture at the Riga Polytechnical Institute and engineering at Moscow’s Highest Technical School completing his PhD studies in 1917. During his stays at home in Reval, he attended the art studio of the famed painter Ants Laikmaa, but even though he showed promise, there are no records that he ever exhibited.

During the German occupation in 1918, Rosenberg served as a teacher at the Gustav Adolf Gymnasium. He gave his first speech on Jewish Marxism on 30 November, at the House of the Blackheads, after the outbreak of the Estonian War of Independence. He emigrated to Germany with the retreating imperial army, along with Max Scheubner-Richter, who served as something of a mentor to Rosenberg and to his ideology. Arriving in Munich, he contributed to Dietrich Eckart’s publication, the Völkischer Beobachter (Ethnic/Nationalist Observer). By this time, he was both an antisemite – influenced by Houston Stewart Chamberlain’s book The Foundations of the Nineteenth Century, one of the key proto-Nazi books of racial theory – and an anti-Bolshevik. Rosenberg became one of the earliest members of the German Workers’ Party – later renamed the National Socialist German Workers’ Party, better known as the Nazi Party – joining in January 1919, eight months before Adolf Hitler joined in September. According to some historians, Rosenberg had also been a member of the Thule Society, along with Eckart, although Nicholas Goodrick-Clarke contends that they were only guests. After the Völkischer Beobachter became the Nazi party newspaper in December 1920, Rosenberg became its editor in 1923. Rosenberg was a leading member of Aufbau Vereinigung, Reconstruction Organisation, a conspiratorial organisation of White Russian émigrés which had a critical influence on early Nazi policy.

In his 1920 book Immorality in the Talmud, Rosenberg identified Jews with the Antichrist. He rejected Christianity for its universality, for its doctrine of original sin (at least for Germans who he declared on one occasion were born noble), and for its teachings on the immortality of the soul, saying, “indeed, absorbing Christianity enfeebled a people.” Publicly, Rosenberg affected to deplore Christianity’s degeneration owing to Jewish influence. Following Chamberlain’s ideas, he condemned what he called “negative Christianity” (the orthodox beliefs of Protestant and Catholic churches), arguing instead for a so-called “positive” Christianity based on Chamberlain’s argument that Jesus was a member of an Indo-European, Nordic enclave resident in ancient Galilee who struggled against Judaism. Significantly, in his work explicating the Nazi intellectual belief system, The Myth of the Twentieth Century, Rosenberg cryptically alludes to and lauds the early Christian heretic Marcion (who rejected the Old Testament as well as the notion of Christ as the Jewish Messiah) and the Manichaean-inspired, “Aryo-Iranian” Cathari, as being the more authentic interpreters of Christianity versus historically dominant Judaeo-Christianity; moreover these ancient, externally Christian metaphysical forms were more “organically compatible with the Nordic sense of the spiritual and the Nordic ‘blood-soul’.” For Rosenberg, the anti-intellectual, religious doctrine was inseparable from serving the interests of the Nordic race, connecting the individual to his racial nature. Rosenberg stated that “The general ideas of the Roman and of the Protestant churches are negative Christianity and do not, therefore, accord with our (German) soul.” His support for Luther as a great German figure was always ambivalent.

In 1923, after the failed Beer Hall Putsch, Hitler, who had been imprisoned for treason, appointed Rosenberg as the leader of the Nazi movement, a position he held until Hitler’s release. Hitler remarked privately in later years that his choice of Rosenberg, whom he regarded as weak and lazy, was strategic; Hitler did not want the temporary leader of the Nazis to become too popular or hungry for power, because a person with either of those two qualities might not want to cede the party leadership after Hitler’s release. However, at the time of the appointment Hitler had no reason to believe that he would soon be released, and Rosenberg had not appeared weak, so this may have been Hitler reading back into history his dissatisfaction with Rosenberg for the job he did.

In 1929 Rosenberg founded the Militant League for German Culture. He later formed the “Institute for the Study of the Jewish Question”, the first branch of a projected Advanced School of the NSDAP, dedicated to identifying and attacking Jewish influence in German culture and to recording the history of Judaism from a radical nationalist perspective. He became a Reichstag Deputy in 1930 and published his book on racial theory The Myth of the Twentieth Century (Der Mythus des 20. Jahrhunderts) which deals with key issues in the Nazi ideology, such as the “Jewish question.” Rosenberg intended his book as a sequel to Houston Stewart Chamberlain’s above-cited book. Despite selling more than a million copies by 1945, its influence within Nazism remains doubtful. It is often said to have been a book that was officially venerated within Nazism, but one that few had actually read beyond the first chapter or even found comprehensible. Hitler called it “stuff nobody can understand” and disapproved of its pseudo-religious tone.

Throughout the trial, it was agreed that Rosenberg had a decisive role in shaping Nazi philosophy and ideology. Examples include: his book Myth of the Twentieth Century, which was published in 1930, where he incited hatred against “Liberal Imperialism” and “Bolshevik Marxism”; furthering the influence of the “Lebensraum” idea in Germany during the war; facilitating the persecution of Christian churches and the Jews in particular; and opposition to the Versailles Treaty.

The following year, once Hitler had become Chancellor, Rosenberg was named leader of the Nazi Party’s Foreign Policy Office in April, and on 2 June 1933 he was named a Reichsleiter, the second highest political rank in the Nazi Party. Another event of 1933 was Rosenberg’s visit to Britain, intended to give the impression that the Nazis would not be a threat and to encourage links between the new regime and the British Empire. It was a notable failure. When Rosenberg laid a wreath bearing a swastika at the Cenotaph, a Labour Party candidate slashed it and later threw it in the Thames and was fined 40 shillings for willful damage at Bow Street magistrate’s court. In January 1934 Hitler granted Rosenberg responsibility for the spiritual and philosophical education of the Party and all related organizations.

In January 1934 Hitler had appointed Rosenberg as the cultural and educational leader of the Reich. The Sanctum Officium in Rome recommended that Rosenberg’s Myth of the Twentieth Century be put on the Index Librorum Prohibitorum (list of books forbidden by the Catholic Church) for scorning and rejecting “all dogmas of the Catholic Church, indeed the very fundamentals of the Christian religion”. During World War II Rosenberg outlined the future envisioned by the Hitler government for religion in Germany, with a thirty-point program for the future of the German churches. Among its articles:

The Hungarian-Jewish journalist Franz Szell, who was apparently residing in Tilsit, Prussia, Germany, spent a year researching in Latvian and Estonian archives before publishing an open letter in 1936, with copies to Hermann Göring, Joseph Goebbels, Foreign Minister Konstantin von Neurath and others, accusing Rosenberg of having “no drop of German blood” flowing in his veins. Szell wrote that among Rosenberg’s ancestors were only “Latvians, Jews, Mongols, and French.” As a result of his open letter, Szell was deported by Lithuanian authorities on 15 September 1936. His claims were repeated in the 15 September 1937 issue of the Vatican newspaper L’Osservatore Romano. Alfred Rosenberg was indeed of Baltic German, French, and probably also of Estonian and Latvian descent, but no Jewish ancestry has been discovered.

In 1940 Rosenberg was made head of the Hohe Schule (literally “high school”, but the German phrase refers to a college), the Centre of National Socialist Ideological and Educational Research, out of which the Einsatzstab Reichsleiter Rosenberg (Reichsleiter Rosenberg Taskforce) developed for the purpose of looting art and cultural goods. The ERR were especially active in Paris in looting art stolen from famous Jewish families such as the Rothschilds and that of Paul Rosenberg. Hermann Göring used the ERR to collect art for his own personal gratification. He created a “Special Task Force for Music” (Sonderstab Musik) to collect the best musical instruments and scores for use in a university to be built in Hitler’s home town of Linz, Austria. The orders given to the Sonderstab Musik were to loot all forms of Jewish property in Germany and of those found in any country taken over by the German army, and any musical instruments or scores were to be immediately shipped to Berlin.

Following the invasion of the USSR, Rosenberg was appointed head of the Reich Ministry for the Occupied Eastern Territories (Reichsministerium für die besetzten Ostgebiete) on 17 July 1941. Alfred Meyer served as his deputy and represented him at the Wannsee Conference. Another official of the Ministry, Georg Leibbrandt, also attended the conference, at Rosenberg’s request.

Amongst other things, Rosenberg issued a series of posters announcing the end of the Soviet collective farms (kolkhoz). He also issued an Agrarian Law in February 1942, annulling all Soviet legislation on farming and restoring family farms for those willing to collaborate with the occupiers. But decollectivisation conflicted with the wider demands of wartime food production, and Hermann Göring demanded that the collective farms be retained, save for a change of name. Hitler himself denounced the redistribution of land as “stupid”.

Rosenberg was captured by Allied troops on 19 May 1945 in Flensburg-Mürwik. He was tried at Nuremberg and found guilty of all four counts: conspiracy to commit crimes against peace; planning, initiating and waging wars of aggression; war crimes; and crimes against humanity. The final judgment against him named him one of the principal planners of the invasions of Norway and the Soviet Union. It also held him directly responsible for the systematic plunder of the occupied countries of Europe, as well as the brutal conditions in Eastern Europe. During his trial he wrote his memoirs, which were published posthumously and with analytical commentary by Serge Lang and Ernst von Schenck.

During the Nuremberg trials, Rosenberg’s handwritten diary was translated by Harry Fiss, Chief of Documentation for the American prosecution. After its use in evidence during the Nuremberg trials, the diary went missing, along with other material which had been given to the prosecutor Robert Kempner (1899–1993). It was recovered in Lewiston, N.Y., on 13 June 2013. Written on 425 loose-leaf pages, with entries dating from 1936 through 1944, it is now the property of the United States Holocaust Memorial Museum (USHMM) in Washington. Henry Mayer, the museum’s senior archivist, and the son of a Holocaust survivor, was able to access the material and while “not given enough time to read [the] diary entry from beginning to end,” he “could see that Rosenberg focused on certain subjects, including brutality against Jews and other ethnic groups and forcing the civilian population of occupied Russia to serve Germany.” Meyer also noted Rosenberg’s “hostile comments about Nazi leaders,” which he described as “unvarnished.” While some parts of the manuscript had been previously published, the majority had been lost for decades. Former Federal Bureau of Investigation agent Robert King Wittman, who helped track down the diary, said, “there is no place in the diary where we have Rosenberg or Hitler saying the Jews should be exterminated, all it said was ‘move them out of Europe'”. The New York Times said of the search for the missing manuscript that “the tangled journey of the diary could itself be the subject of a television mini-series.” Since the end of 2013, the USHMM has shown the 425-page document (photos and transcripts) on its homepage.