The death of Keith Campbell was announced by officials at the University of Nottingham, where Campbell had taught since 1998.
He was 58. The cause of his death wasn't made public, The New York Times reported.
In February 1997, Campbell and his colleague Ian Wilmut, both then on the staff of a research center near Edinburgh, Scotland, announced that Dolly, the first mammal to be cloned from an adult animal, had been born in Scotland the summer before.
The announcement caused considerable controversy, including concerns it might lead to human cloning. After Dolly's birth, human reproductive cloning was banned in several countries, including Canada and Australia, and in a number of U.S. states.
In 2005, the United Nations adopted a nonbinding declaration calling for its members to prohibit human cloning in any form.
Campbell said human cloning was a distant possibility and that he was against the idea.
He earned a bachelor's degree in microbiology from the University of London in 1978, followed in 1986 by a doctorate from the University of Sussex, and joined the staff of the Roslin Institute in Edinburgh, where Dolly was cloned, in 1991.
Dolly, who suffered from arthritis and lung ailments, was euthanized in 2003.