The International Socialist Organization (ISO) was a political group in the United States that advocated for socialist principles and Marxist theory. Founded in 1977, the ISO aimed to build a revolutionary socialist movement and was involved in various social justice issues, including labor rights, anti-racism, and anti-war activism. The organization published a magazine called Socialist Worker and participated in numerous protests and campaigns. The ISO emphasized the importance of grassroots organizing and sought to unite workers and marginalized communities to challenge capitalism and promote social change. It dissolved in 2019, citing internal disagreements and challenges in maintaining its structure.