Sinesio Baudillo García Fernández (20 May 1897 – 18 October 1983), commonly known by his pseudonym Diego Abad de Santillán, was a Spanish Argentine anarcho-syndicalist economist.

[5] In the Spanish capital, he began to live a bohemian lifestyle,[2] taking the pseudonym Diego Abad de Santillán while writing for dissident journals.

[4] In Spain, Santillán joined the Confederación Nacional del Trabajo (CNT) and became secretary of the Iberian Anarchist Federation (FAI), for which he edited their respective newspapers Solidaridad Obrera and Tierra y Libertad.

Following the outbreak of the Spanish Civil War, he joined the Central Committee of Antifascist Militias of Catalonia and was appointed Minister of Economy in the Catalan government.

[7] In the wake of the May Days, he took a critical line against the government of Juan Negrín and the Communist Party of Spain (PCE),[5] publishing After the Revolution, which outlined a program for workers' self-management under anarcho-syndicalism.

We want a socialized economy in which the land, the factories, the homes, the means of transport cease to be the monopoly of private ownership and become the collective property of the entire community.When the Republic was defeated, Santillán fled into exile in France, before finally returning to Argentina.