Humankind faces a growing spectrum of anthropogenic existential threats to human civilization and survival. This article therefore aims to develop a new framework for security policy – ‘existential security’ – that puts the survival of humanity at its core. It begins with a discussion of the definition and spectrum of ‘anthropogenic existential threats’, or those threats that have their origins in human agency and could cause, minimally, civilizational collapse, or maximally, human extinction. It argues that anthropogenic existential threats should be conceptualized as a matter of ‘security’, which follows a logic of protection from threats to the survival of some referent object. However, the existing frameworks for security policy – ‘human security’ and ‘national security’ – have serious limitations for addressing anthropogenic existential threats; application of the ‘national security’ frame could even exacerbate existential threats to humanity. Thus, the existential security frame is developed as an alternative for security policy, which takes ‘humankind’ as its referent object against anthropogenic existential threats to human civilization and survival.