Richard D. Ryder (born 1940) is a British psychologist who, after performing psychology experiments on animals, began to speak out against the practice, and became one of the pioneers of the modern animal liberation movement. He was Mellon Professor at Tulane University, New Orleans, and is the author of Painism: A Modern Morality and Putting Morality Back into Politics, due to be published in 2006.

A former chairman of the Royal Society for the Prevention of Cruelty to Animals council, and a past president of Britain's Liberal Democrat Animal Protection Group, he is parliamentary consultant to the Political Animal Lobby as of April 2004.

Ryder was a contributor to the influential Animals, Men and Morals: An Inquiry into the Maltreatment of Non-humans (1972) edited by Roslind and Stanley Godlovitch and John Harris. It was in a review of this book for the New York Review of Books that Peter Singer put forward the basic arguments, based on utilitarianism, that in 1975 became Animal Liberation, the book often referred to as the "bible" of the animal rights movement.