William MacAskill (born William Crouch; March 24, 1987) is a Scottish philosopher, ethicist, and notable figure within the effective altruism movement. He is Co-Principal Investigator of the Programme on the Philosophical Foundations of Effective Altruism at the Future of Humanity Institute at Oxford. MacAskill is the founder and president of 80,000 Hours, the co-founder and vice-president of Giving What We Can, and the author of Doing Good Better.