Steiner was the Administrator of the UN Development Programme (UNDP) between 2017-2025. Prior to that, 2006-2016, he led the United Nations Environment Programme (UNEP).

He has also served as Director-General of the UN Office in Nairobi, Kenya, as Director General of the International Union for the Conservation of Nature, and Secretary General of the World Commission on Dams. Before leading UNDP, Steiner was Director of the Oxford Martin School and Professorial Fellow of Balliol College at the University of Oxford. 

Born in 1961, Steiner has a bachelor’s degree from the University of Oxford and a master’s degree from the University of London, specializing in development economics, regional planning, and international development and environment policy.  He also studied at the German Development Institute and at the Harvard Business School.