Mark O’Neill is a senior executive at the U.S. Department of Health and Human Services, where he serves as Chief of Staff in the Administration for Strategic Planning and Response. A retired U.S. Army Colonel with nearly 27 years of distinguished service, Mr. O’Neill brings extensive leadership experience in crisis response, interagency coordination, and international engagement. His military career included brigade command, command of a multinational battlegroup, battalion command, operational deployments to multiple countries, and key policy roles at the Pentagon and on Capitol Hill. He has served as a strategist, legislative liaison, and executive officer at the highest levels of the Department of Defense. Mr. O’Neill holds a bachelor’s degree from Villanova University and master’s degrees from George Washington University and the U.S. Army War College. He is widely recognized for his ability to build coalitions, lead diverse teams, and integrate operations across complex systems, skills that now support the health and security of the American public.