This chapter discusses the UK system of town and country planning, which plays a central role in environmental law because of its enormous importance in relation to locational issues, as well as in determining how much of any particular activity is allowed in any place and the intensity of such development. However, town and country planning is not only about environmental protection: it has a wider role in organizing economic development. In balancing economic, political, social, and environmental factors to do with development in a democratic context, it ought to be a key mechanism for making development more sustainable. The chapter deals with town and country planning law, rather than the role of planning-type mechanisms in general. The law now requires various plans relating to the environment, such as the national strategies for air and waste, and river basin plans for water quality regulation, while there are also non-statutory plans, such as local transport plans, and informal plans, such as local Environment Agency plans.