William David MacAskill, born March 24, 1987, is a Scottish philosopher and ethicist at the University of Oxford, where he served as a Research Fellow at the Global Priorities Institute. He is recognized as one of the originators of the effective altruism movement and co-founded pivotal organizations including Giving What We Can in 2009, the Centre for Effective Altruism, and 80,000 Hours, which provide guidance on high-impact career choices and charitable giving. His notable publications include 'Doing Good Better' (2015), which popularized effective altruism principles; 'What We Owe the Future' (2022), advocating for longtermism; and co-authorship of 'Moral Uncertainty' (2020). MacAskill's work emphasizes using evidence and reason to do the most good, influencing philanthropists and policymakers globally.