Republican federalist politician. He was also a lawyer, journalist, writer, philosopher and historian. He obtained a doctorate in Law in 1848.

Pi i Margall was influenced by the writings of Pierre-Joseph Proudhon and believed in socialist democracy and libertarian socialism. He translated into Spanish Proudhon’s Philosophie du progrès and Du principe fédératif while exiled in Paris. It is said that these translations impacted the formation of anarchism in Spain. Besides Proudhon, he was influenced by Hegel’s and Rousseau’s writings. He opposed virulently the Spanish monarchy and participated to several revolutions: in 1854, in 1868, for example. His opposition to the monarchy led him to oppose the 1869 monarchical-democratic Constitution. He incessantly fought for the establishment of a federal republic and defended the liberty of the press, of education, of association, among others.

Pi was one of the most important leaders of the Republican federalist movement after the 1868 Gloriosa Revolution. He became the second president of the First Spanish Republic in 1873 and defended the project of a Federal Constitution for Spain, which was never enacted. While president, he developed a program of reforms: separation of the Church and the State, abolition of slavery, free and mandatory education, repartition of the land, limitation of child labor, right of association, liberty of working-class association, among others. He resigned on July 18, 1873.

Pi i Margall was jailed and exiled (to France) for his ideas and his conspiracies against the monarchy. He wrote a great number of newspapers articles in El Correo, La Razón, La Discusión, El nuevo régimen, among others. Some of his writings were censured, among them Historia de la pintura and Estudios sobre la Edad Media because of his criticism of religion. His study La República de 1873 was condemned as well.

His book La reacción y la revolución explores radical democratic ideas according to which the revolution should be organized by the popular classes and popular sovereignty is to be defended. He published on working class issues and collaborated with working class organizations.

Pi defended the Cuban independence in his writings in El nuevo regimen.