The Internal Macedonian Revolutionary Organization (United) (1925–1936) (Macedonian: Внатрешна македонска револуционерна организација (обединета), Vnatrešna makedonska revolucionerna organizacija (obedineta); Bulgarian: Вътрешна македонска революционна организация - обединена, Vatreshna makedonska revolyucionna organizatsiya - Obedinena), commonly known in English as IMRO (United), was the name of a revolutionary political organization active across the entire geographical region of Macedonia.
IMRO (United) was founded in 1925 in Vienna after the failure of the May Manifesto by the left wing of the Internal Macedonian Revolutionary Organization (IMRO). It was under the leadership of Dimitar Vlahov, Pavel Shatev, Georgi Zankov, Rizo Rizov, Vladimir Poptomov, Metodi Shatorov and Hristo Yankov. Its main objective was to free Macedonia within its geographical and economical borders, and to create a new political entity which would become an equal member of the future Balkan Federative Republic. It was accepted as a partner in the Balkan Communist Federation and was sponsored directly by the Comintern, maintaining close links with the Bulgarian communist leader Georgi Dimitrov. He, as secret agent of GRU was responsible especially about the contacts with the IMRO (United).
The Resolution of the Comintern publicly acknowledged the existence of the Macedonian nation and Macedonian language, although published as a resolution of the Internal Macedonian Revolutionary Organization (United), was undoubtedly the most significant international acknowledgement of the Macedonian national individuality, which had very favorable consequences for its development and affirmation. The text of this historic document was prepared in the period between December 20, 1933 and January 7, 1934 by the Balkan Secretariat of the Comintern. It was accepted by the Political Secretariat in Moscow on January 11, 1934, and approved by the Executive Committee of the Comintern. It was published for the first time in the April issue of Makedonsko Delo under the title "The Situation in Macedonia and the Tasks of IMRO (United)". After replying to those who, even within the progressive movement, denied the existence of a separate Macedonian nation, the Resolution, among other things, stated: