Dian Fossey was an American zoologist known world wide for her championing the cause of Mountain Gorillas. Fossey caught her first glimpse of Mountain Gorillas in 1963 on a field trip to East Africa, when she also met Louis Leakey. It was Leakey who persuaded Fossey to return to Africa and make a long-term study of the Gorillas.
After poachers killed one of Fossey's favorite gorillas, Digit, she dedicated her time to campaigning against the encroachment of gorilla territory and their slaughter by poachers. In the early 80s Fossey took a visiting professorship at Cornell University, where she completed Gorillas in the Mist (made into a film staring Sigourney Weaver).
On return to Rwanda, she stepped up the level of her campaigning against poaching. On 26 December 1985 her body was discovered near her campsite. No one has ever been brought to justice for her murder.
For more on Dian Fossey
Dian Fossey Biography from About.com's Guide to Women's History