Dian Fossey was an American anthropologist who is best known for her work with mountain gorillas in Rwanda. She studied under anthropologist Margaret MEAD and worked with paleoanthropologist Louis Leakey. Fossey's research focused on the behavior of APES, specifically the mountain GORILLA, and she was the first to document the complex social structure of these primates. Her work helped to bring attention to the plight of endangered species and conservation efforts.