Grandizo Munis (1912-1989) was a Spanish politician.

Grandizo first entered revolutionary politics as a member of the Izquierda Comunista Espana (ICE) or Left Communists of Spain. This group was led by Andres Nin and was in sympathy with the views of Leon Trotsky and therefore affiliated to the International Communist League.

Trotsky was opposed to the name of the group which he argued was imprecise and badly expressed the program of the Bolshevik-Leninists. In addition he entered into dispute with Nin and the ICE when they refused his suggestion to enter the youth organisation of the Spanish Socialist Workers Party (PSOE). The majority of the ICE then split with Trotsky leaving a small remnant grouping which included Grandizo Munis.

With the beginning of the Spanish Civil War in 1936 Munis was a member of the tiny Seccion Bolshevik-Leninista. This organisation sought to influence the ranks of the larger Workers Party of Marxist Unification (POUM) and also worked closely with the more left wing anarchists of the Durruti Column.

The Trotskyists were among the very few to oppose the Popular Front government and openly took part in the May Days of 1937. This event led to their suppression by the government which was now dominated by the Stalinists. This meant that Munis was forced into illegality and had to flee for fear of his life.

Eventually Munis found refuge in Mexico where he continued his activism in the Trotskyist movement alongside other Spanish exiles. He also became a close friend of Natalya Sedova, the widow of Leon Trotsky. However he began to develop differences with the majority of the Trotskyist movement and wrote several critiques of the leadership of the Fourth International. In particular he criticised James P. Cannon and the American Trotskyists' attiude to the war as expressed in their trial testimony in the book Socialism On Trial.

Following the war Munis' critique becme even more marked and he wrote a strong document which argued that the Fourth International was in danger of political collapse. He argued that this was because it failed to realise that the Russian state had become capitalist and was now counter-revolutionary. As a result of these differences he left the Fourth International along with a small band of sympathisers including the French surrealist poet and activist Benjamin Peret.

Eventually, after a period which he spent jailed for revolutionary activity in Spain, Munis founded Forment Ouvrier Revolutionaire (FOR), a small revolutionary organisation espousing his views. FOR would find supporters in Spain, France, Greece and in the USA. But by the time of Munis death was a tiny grouping.

Munis wrote many articles and books in his life, the best known being A Second Communist Manifesto and a history of the Spanish Civil War which remains untranslated into English.