Social sustainability is the least defined and least understood of the different ways of approaching sustainability and sustainable development. Social sustainability has had considerably less attention in public dialogue than economic and environmental sustainability.

There are several approaches to sustainability. The first, which posits a triad of environmental sustainability, economic sustainability, and social sustainability, is the most widely accepted as a model for addressing sustainability. The concept of "social sustainability" in this approach encompasses such topics as: social equity, livability, health equity, community development, social capital, social support, human rights, labour rights, placemaking, social responsibility, social justice, cultural competence, community resilience, and human adaptation.

A second, more recent, approach suggests that all of the domains of sustainability are social: including ecological, economic, political and cultural sustainability. These domains of social sustainability are all dependent upon the relationship between the social and the natural, with the "ecological domain" defined as human embeddedness in the environment. In these terms, social sustainability encompasses all human activities. It is not just relevant to the focussed intersection of economics, the environment and the social. (See the Venn diagram and the Circles of Sustainability diagram).