This monograph reviews the state of the third sector in both Australia and Aotearoa New Zealand, and is the first comprehensive overview of the research that has studied and documented it. While the third sector/civil society has existed in Australasia since the beginning of colonial times and before, the major flowering in practice and research has occurred after 1990; the monograph therefore mainly focusses on developments since that time. Part One begins with an overview of the scope and scale of the sector in society, and how it is defined. It also reviews the infrastructure that has developed to monitor, support and research the sector. Part Two examines the sector’s relationship with the State, rapid increases in funding the ‘purchase-of-services’ under neo-liberal ideological and policy constraints. Part Three documents the current state of volunteering and philanthropy. Part Four examines the large but often less documented realm of citizen action, building social cohesion and social capital, advocacy, and protest. Part Five considers newly emerging third sector forms, and challenges for the future.