Corneliu Zelea Codreanu (; September 13, 1899 – November 30, 1938) — born Corneliu Zelinski and commonly known as Corneliu Codreanu — was a Romanian politician of the far right, the founder and charismatic leader of the Iron Guard or The Legion of the Archangel Michael (also known as the Legionary Movement), an ultra-nationalist and violently antisemitic organization active throughout most of the interwar period. Generally seen as the main variety of local fascism, and noted for its mystical and Romanian Orthodox-inspired revolutionary message, it grew into an important actor on the Romanian political stage, coming into conflict with the political establishment and the democratic forces, and often resorting to terrorism. The Legionaries traditionally referred to Codreanu as Căpitanul ("The Captain"), and he held absolute authority over the organization until his death.
Codreanu, who began his career in the wake of World War I as an anticommunist and antisemitic agitator associated with A. C. Cuza and Constantin Pancu, was a co-founder of the National-Christian Defense League and assassin of the Iaşi Police prefect Constantin Manciu. Codreanu left Cuza to found a succession of movements on the far right, rallying around him a growing segment of the country's intelligentsia and peasant population, and inciting pogroms in various parts of Greater Romania. Several times outlawed by successive Romanian cabinets, his Legion assumed different names and survived in the underground, during which time Codreanu formally delegated leadership to Gheorghe Cantacuzino-Grănicerul. Following Codreanu's instructions, the Legion carried out assassinations of politicians it viewed as corrupt, including Premier Ion G. Duca and its former associate Mihai Stelescu. In parallel, Corneliu Zelea Codreanu advocated Romania's adherence to a military and political alliance formed around Nazi Germany.
He registered his main electoral success during the 1937 suffrage, but was blocked out of power by King Carol II, who came to favor rival fascist alternatives around the National Christian Party and the National Renaissance Front. The rivalry between, on one side, Codreanu, and, on the other, Carol and moderate politician Nicolae Iorga ended in the former's imprisonment at Jilava and assassination at the hands of the Gendarmerie. He was succeeded as leader by Horia Sima. In 1940, under the National Legionary State proclaimed by the Iron Guard, his killing served as the basis for violent retribution.
Corneliu Zelea Codreanu's views influenced the modern far right. Groups claiming him as a forerunner include Noua Dreaptă and other Romanian successors of the Iron Guard, the International Third Position, and various neofascist organizations in Italy and other parts of Europe.