The fossil fuel divestment movement is at the forefront of civil society initiatives to raise public consciousness about the need for a "fossil-free" future. Through the lens of the social movement literature, this article shows how the movement has harnessed grassroots activists, engaged in innovative and sometimes disruptive forms of protest, and used cognitive framing and symbolic politics to gain media interest and persuade the public of the importance and legitimacy of its claims as well as to promote a new social norm. The relative instrumental, structural, and discursive power of the movement and its adversaries is also examined, showing how, notwithstanding the fossil fuel industry's deeply embedded structural and instrumental power, the movement has managed to shift the contest onto a terrain where it holds a comparative advantage. Finally, the movement's role in nonstate climate governance is considered, taking account of its interactions with and impact on a range of other climate actors. This article's conclusion is that climate governance is not only an instrumental or pragmatic process of mandating changes in behavior but an expressive and symbolic one of nurturing a new norm and institutionalizing a new set of moral principles.