Achim Steiner (born 1961 in Brazil) is a German expert in environmental politics. From 2001 to 2006 he was Director General of the International Union for Conservation of Nature and Natural Resources (IUCN). Since June 2006 he has been Executive Director of the United Nations Environment Programme (UNEP).
Acting on the nomination of Secretary-General Kofi Annan, the UN General Assembly unanimously elected Steiner as the Executive Director of UNEP on 16 March 2006 for a four-year term, effective 15 June 2006. In this office he succeeded Klaus Töpfer. He became the fifth Executive Director in UNEP's history. Effective as of 1 March 2009, Achim was also appointed Director-General of the UN Offices at Nairobi (UNON).
At its 83rd plenary meeting, on 22 April 2010, the General Assembly, on the proposal of the Secretary-General, re-elected Steiner as Executive Director of the United Nations Environment Programme for another four-year term of office beginning on 15 June 2010 and ending on 14 June 2014.