The long-term sustainability of space activities is an emerging issue to which actors in the global space community –including governments, agencies, and industry– are devoting increasing amounts of attention and resources. Considering the sustainability of space activities involves taking into account the present population of space debris, the size of the debris population in the most commonly-used Earth orbits in the future, and the possibility of collision events between objects in space. Addressing space debris and other threats to space sustainability involves both technological and political solutions. The United Nations Committee on the Peaceful Uses of Outer Space (copuos) has led a major effort to define such solutions and has established a working group tasked with the development of non-binding long-term sustainability (lts) guidelines. This article includes an overview of the concept of space sustainability, a discussion of the need, development, and current status of the lts guidelines, as well as an analysis of some of the guidelines themselves. It concludes with a broader discussion of space as an area without state sovereignty – one of the key aspects that have influenced the development of non-binding measures to address the space sustainability challenge. In this context, and given the governance questions that arise from the interaction between states and non-state actors in this domain, this discussion should be of interest to international relations scholars and practitioners.