This article analyses gender mainstreaming as a new and essentially contested form of feminist politics and policy. The article addresses the different forms that gender mainstreaming takes, in different countries and different policy domains, in order to push forward the theoretical debates. Gender mainstreaming often draws on transnational processes, involving transnational networks and agencies and transformations of the discourse of universal human rights, challenging the traditional focus on national processes. These developments are facilitated by the rise of global processes and institutions, such as the UN. Tensions can arise as a result of actors seeking to mainstream quite different models of gender equality: based on equality through sameness; through equal valuation of difference; and through transformation. The intersection of gender with other complex forms of inequality has challenging implications for a primary focus on gender within gender mainstreaming. Nevertheless, certain forms of gender mainstreaming have, despite their evident weaknesses, provided a new basis for feminist solidarity and action at a global level. Gender mainstreaming is a leading-edge example of the potential implications of globalisation for gender politics.