Sustainable development is a concept with popular currency and use in international, regional, and national application through various legal and policy instruments and initiatives. It applies generally to balance social, economic, and environmental objectives in decision-making. This chapter presents an overview of this international concept bringing out the contested debate and interpretations on its meaning in the legal and policy instruments and scholarly literature. It locates sustainable development in its context of key sub principles that reflect the three main dimensions and objectives of sustainability: the economic, the environmental, and the social. The key principles examined are the polluter pays principle (relating to economic aspects), the precautionary principle (relating to environmental aspects), and the principle of public participation (relating to social aspects). The analysis here is intended to establish a framework for understanding the concept, and its legal and policy context, and for its practical application through the sub-principles at the regional or domestic level. 1 It will show that despite the definitional questions, sustainable development has direct and primary relevance for regulating economic activities for environmental protection, alongside the competing need for ensuring developmental sustainability and will put in context the definitional challenges of implementing sustainability at the EU level which are considered subsequently.