Environmental law is a complex and interlocking body of treaties, conventions, statutes, regulations, and common law that operates to regulate the interaction of humanity and the natural environment, toward the purpose of reducing the impacts of human activity.

The topic may be divided into two major subjects: pollution control and remediation, and resource conservation and management. Laws dealing with pollution are often media-limited—i.e., pertain only to a single environmental medium, such as air, water (whether surface water, groundwater or oceans), soil, etc.—and control both emissions of pollutants into the medium, as well as liability for exceeding permitted emissions and responsibility for cleanup. Laws regarding resource conservation and management generally focus on a single resource, e.g., natural resources such as forests, mineral deposits or animal species, or more intangible resources such as especially scenic areas or sites of high archeological value, and provide guidelines for and limitations on the conservation, disturbance and use of those resources. These areas are not mutually exclusive—for example, laws governing water pollution in lakes and rivers may also conserve the recreational value of such water bodies. Furthermore, many laws that are not exclusively "environmental" nonetheless include significant environmental components and integrate environmental policy decisions. Municipal, state and national laws regarding development, land use and infrastructure are examples.