Small region sustainability is an extremely important part of the journey to sustainability of the global population, as the most difference can be made at this spatial level through decision making and community choice. However, small regions have not been the focus of sustainability literature. Therefore, this thesis develops theory to explain what small region sustainability involves and tested the applicability of current sustainability assessment methods to find an effective tool for the journey to sustainability that can be used for social learning, decision making, policy development, research and monitoring of sustainability in small regions. It was found through the development of a model of sustainable carrying capacity and the major pressures of human activities on the environment, that sustainability for small regions means living equitably with the impacts of human activities in the region within the limits of its ecosystems. This thesis also found that none of the current sustainability methods tested were effective or useful as a tool for small regions. Therefore, a new sustainability assessment method was developed, the Sustainable Carrying Capacity Assessment (SCCA), which assesses the equitability and size of the major pressures that the human activities are causing and determines if this pressure exceeds the sustainable carrying capacity of the region, and thus, the sustainability of the population. Thus, for small regions to become sustainable, they must live equitably within the sustainable carrying capacity of the region's ecosystems, and a tool that can help them achieve this is the SCCA. By raising social awareness, guiding policy development and decision making this method can help guide small regions, and other spatial levels on their journey to sustainability. Therefore, it is recommended that Local Government Areas, Regional Organisation of Councils, schools, local community groups and anyone who wants to learn more about sustainability use this method. This thesis, therefore, makes a significant contribution to the field of sustainability.