The year 2010 was the centennial of Clara Zetkin's proposal for an annual women's holiday, which became known as International Women's Day, and 2011 was the centennial of its first celebrations. The first ten years of the holiday's existence were a particularly tumultuous time in world history, with the advent of World War I, revolutionary upheavals in some of the major combatant countries, and the demise of the German, Habsburg, Ottoman, and Russian empires. During this time, International Women's Day celebrations quickly gained great popularity, and in 1917 sparked the February Russian Revolution. This article focuses on the development of the holiday from its U.S. and Western European origins and goal of women's suff rage, to its role in empowering Russian women to spark a revolution, and its re-branding as a Soviet communist celebration. Special attention is paid to the roles of two prominent international socialist women leaders, Zetkin and Alexandra Kollontai, in shaping the holiday's evolution.