Peter Albert David Singer (born July 6, 1946) is an Australian philosopher. He is the Ira W. DeCamp Professor of Bioethics at Princeton University, and laureate professor at the Centre for Applied Philosophy and Public Ethics (CAPPE), University of Melbourne. He specializes in applied ethics, approaching ethical issues from a secular preference utilitarian perspective.

He has served, on two occasions, as chair of philosophy at Monash University, where he founded its Centre for Human Bioethics. In 1996, he ran unsuccessfully as a Green candidate for the Australian Senate. In 2004, he was recognized as the Australian Humanist of the Year by the Council of Australian Humanist Societies.

Outside academic circles, Singer is best known for his book Animal Liberation, widely regarded as the touchstone of the animal liberation movement. Not all members of the animal liberation movement share this view, and Singer himself has said the media overstates his status. His views on that and other issues in bioethics have attracted attention and a degree of controversy.