In the face of insufficient progress in conserving and restoring biodiversity, the in situ use of advanced genetic modification, gene drives, and other biotechnologies for conservation purposes are being considered, researched, and developed. This paper introduces the methods, applications, environmental risks, and social challenges of “conservationist synthetic biology”; reviews existing governance, with an emphasis on international instruments, institutions, and processes; and offers observations of the politics of developing further governance. The most important multilateral environmental agreement is the Convention on Biological Diversity. Governance of such conservationist synthetic biology is vital but gaps remain. The further development of governance is a political process, and conservationist synthetic biology has a political landscape that is atypical for emerging technologies.