John P. Holdren is an American scientist known for his extensive career in academia and public service, notably as the senior advisor to President Barack Obama on science and technology issues. From January 2009 to January 2017, he served concurrently as Assistant to the President for Science and Technology, Director of the White House Office of Science and Technology Policy (OSTP), and co-chair of the President's Council of Advisors on Science and Technology (PCAST).