The world confronts an interlinked ecological, economic, social, and political crisis crystallised in the issue of climate change. The failure of governments acting alone and through international institutions to effectively address the climate crisis has led to the growth of a distinct climate movement within civil society whose broad aim is to bring about the changes required to mitigate anthropogenic global warming. This dissertation examines the role that ecosocialists are playing within the broader climate movement. Utilising a modified neo-Gramscian perspective that builds on the work of Robert Cox and incorporates the global political economy as a category within the Earth's biosphere, the dissertation provides a critical ecological political economy account of the shift from the Holocene to the Anthropocene in the context of post-war, US-led 'neoliberal globalisation.' Building on extensive literature reviews in a range of different discipline areas including the Ecosocialist literature, the dissertation also draws on new primary data in the form of online audio-visual recordings of ecosocialist and scientific meetings and conferences and debates between ecosocialists published on websites. This material is supplemented by interviews with ecosocialists and climate activists undertaken as a participant observer in a number of climate movement‚ÄövÑv™related protest events, including at the 2015 Paris Climate Summit. The study confirms the value of ecosocialists' analyses of the neoliberalising global political Economy that global capitalism does, indeed, result in multiple interconnected ecological, economic, social, and political crises. Focusing specifically on the climate crisis, it describes the origins and operations of the primary institutions established to address anthropogenic global warming (the Intergovernmental Panel on Climate Change and the United Nations Framework Convention on Climate Change) and analyses how the failure of governments working through these institutions to mitigate global warming resulted in the development and growth of the climate movement. Identifying a bifurcation of the movement into a reform-oriented climate action wing and a more system-critical climate justice wing after the 2007 Bali Climate Summit, the dissertation then studies the key role being played by ecosocialists in the movement's more radical climate justice wing. Using Gramscian concepts such as 'war of position,' 'passive revolution' and 'trasformismo,' the dissertation evaluates both the ecosocialist strengths and the challenges these actors face in participating in and influencing the broader climate movement. The study concludes by describing some of the limitations of the approaches adopted inconducting this research, engaging in a personal reflection on the research project, and proposing suggestions for further research.