This article works on the three questions: “How can libraries make an effective contribution to resolving the sustainability challenges we are collectively facing?”; “When are libraries truly sustainable?”; and “How can library management support this shift?”. Looking across libraries and their history of the last decades, the author discerns different stages of development leading to sustainability. In line with the work of Dyllick and Muff (2016) the author describes Sustainability Levels 0.0 to 3.0. The highest level requires a quantum leap and shifts from thinking inside-out to outside-in. This article addresses the need that there is virtually no academic management literature on the topic of sustainability in libraries. It shows that whilst there are many examples of individual projects or activities, there is a serious lack of methodology senior management level.