Trajectories of human conflict have direct and indirect impacts on biodiversity and ecosystem function. These occur across terrestrial, marine and freshwater systems via the well-established drivers of biodiversity loss: land and sea-use change, climate change, overexploitation, pollution and invasive species. However, the mechanisms underlying the nature of some of these connections are still poorly explored, as is the compilation of existing evidence. Furthermore, indirect drivers, spillover effects, and synergistic relationships between drivers are additional knowledge gaps. Building a full picture requires exploring the magnitude and directionality of impacts within the wider context of socioeconomic change and geopolitics with which conflict is associated. As this knowledge advances, conflict in its diverse forms is likely to emerge as the most overlooked and significant indirect driver of biodiversity loss internationally. Additionally, it is our greatest challenge in achieving sustainable development, specifically due to the primacy of its influence on all other sustainability challenges.