A land defender, land protector, or environmental defender is an activist who works to protect ecosystems and the human right to a safe, healthy environment. Often, defenders are members of Indigenous communities who are protecting property rights of ancestral lands in the face of expropriation, pollution, depletion, or destruction.

Environmental defenders or environmental human rights defenders are individuals or collectives who protect the environment from harms resulting from resource extraction, hazardous waste disposal, infrastructure projects, land appropriation, or other dangers. In 2019, the UN Human Rights Council unanimously recognised their importance to environmental protection. The term environmental defender is broadly applied to a diverse range of environmental groups and leaders from different cultures that all employ different tactics and hold different agendas. Use of the term is contested, as it homogenizes such a wide range of groups and campaigns, many of whom do not self-identify with the term and may not have explicit aims to protect the environment.