Peter A. Singer is an Australian philosopher known for his work in ethics and his role in the animal rights movement. He is a professor at Princeton University and is best known for his book, Animal Liberation, published in 1975, which argues against speciesism and advocates for the consideration of animal suffering. Singer is also recognized for his contributions to effective altruism, a philosophy that encourages individuals to use their resources to do the most good. His ideas have influenced discussions on global poverty, bioethics, and environmental issues, making him a prominent figure in contemporary moral philosophy.