Posthuman International Relations calls for a profound re-thinking of the study of international relations. International Relations remains wedded to the enlightenment project of overcoming the hazards of nature, and thus is fully human-centred in its approach. The resultant environmental security perspectives tend to reproduce a dualistic understanding of human relations to 'the environment' in which humans are either threatened by or pose a threat to 'nature'. Whilst we are undoubtedly in a situation of risk, this is shaped by histories of social relations, economic practices and formations of political power. By contract, this book draws on recent advances in thinking about systems derived from complexity theory to develop an analysis of international relations embedded within broader multi-species, and environmental circumstances. In doing so, Cudworth and Hobden suppy the tools for a fundamental re-evaluation of international relations, in particular with regard to environmental issues.