Environmental Defense Fund, American environmental organization working on such issues as climate change, pollution, and endangered wildlife. It was founded in 1967 and successfully fought in the courts for a U.S. ban on the synthetic insecticide DDT. With a staff that includes scientists, economists, and lawyers, the group works with governments, corporations, and communities to find solutions to environmental problems. It lobbies to enact environmental protection laws and fights lawsuits to uphold them.