The Eastern Region Army Group, Spanish: Grupo de Ejércitos de la Región Oriental (GERO), was a military formation of the Spanish Republican Army during the last phase of the Spanish Civil War. It was established in June 1938 as a response to the splitting in two of the territory under the sovereignty of the Spanish Republic after the Central Region Army Group (GERC), under the command of General Miaja, had been set up in the central-southern region of Spain.

The Spanish Republican Army was the main branch of the Armed Forces of the Second Spanish Republic between 1931 and 1939.