Born in Hungary, Geza Teleki emigrated to the United States with his family at the age of six. At the end of a career devoted mainly to the study of chimpanzees, when the onset of multiple organ failures began to seriously affect his quality of life, he returned to Hungary, where he died on Szentendre Island on January 7, 2014. He is survived by his wife, Heather McGiffin, and their son, Aidan. Geza’s involvement with chimpanzees began in 1968, when he persuaded Louis Leakey to send him to work with Jane Goodall, then in the beginning phases of her lifelong study of the chimpanzees of the Gombe Stream Reserve in Tanzania. After two years he returned to study primatology with C. Ray Carpenter at Pennsylvania State University. In 1973 he published “Predatory Behavior in Wild Chimpanzees,” and in the following years he was a co-editor of “Omnivorous Primates: Gathering and Hunting in Human Evolution.” In the late 1970s, Geza’s attention was drawn to Sierra Leone in West Africa, where numbers of applications to export chimpanzees were greater than the estimated population could have sustained. As a result, with World Wildlife Fund support he and Lori Baldwin carried out the first population survey of chimpanzees in Sierra Leone in 1979–1980. This survey convinced Geza that the most important site for chimpanzee conservation in that country was in the Outamba and Kilimi regions in the northwest. He persuaded the World Wildlife Fund to support a proposal to create an Outamba-Kilimi National Park (OKNP) and spent the early 1980s in Sierra Leone directing efforts to establish the park. Practical difficulties and a lack of funds delayed full gazettement of the park until 1995, but OKNP still protects the largest chimpanzee population in Sierra Leone and stands as a lasting testament to Geza’s efforts. Returning to the United States in 1984, Geza concentrated on chimpanzee conservation. His efforts helped to prevent the establishment of a medical research station in Sierra Leone that would use captive chimpanzees. In 1986 he was among the founders of the Committee for the Conservation and Care of Chimpanzees, and later became its chairman. He continued to do free-lance conservation work for the World Wildlife Fund and to make other significant contributions to improve the lot of both wild and captive chimpanzees. Geza was a man of high intelligence with great persuasive abilities. He had a creative imagination, and was never daunted by tasks of great complexity, such as the Outamba-Kilimi National Park. Persistence and determination were characteristic of all his endeavors. Geza had a somewhat skeptical opinion of Homo sapiens in the aggregate, although he had admiration for and warm friendships with many different individuals. He thought much more highly of chimpanzees as a species, in fact, and it was this view that motivated his many successful efforts on their behalf.