This article challenges widespread uncritical portrayals of Rosa Luxemburg. By examining the politics and practices of Luxemburg and her SDKPiL party in Poland, I show that their commitment to proletarian emancipation was undermined by sectarian and doctrinaire tendencies that contributed to the defeat of Poland’s workers’ revolutions in 1905 and 1918–19. A critical analysis of their approaches to the national question, the Polish Socialist Party, German Social Democracy, and the role of the revolutionary party, undermines the prevailing romanticisation of Luxemburg. (...) I argue that the Polish Socialist Party, Luxemburg’s main political rival, posed a viable Marxist alternative for Poland’s revolutionary movement. (shrink)