The International Socialist Party of Subcarpathian Rus' (Russian: Интернациональная социалистическая партия Подкарпатской Руси) was a political party in Subcarpathian Rus', eastern Czechoslovakia. The party was formed in March 1920, by supporters of the now defeated Hungarian Soviet Republic and prisoners of war having returned from Soviet Russia.[1][2][3] The party was one of the forerunners of the Communist Party of Czechoslovakia.