Sanjaasuren Oyun (Mongolian: Санжаасүрэнгийн Оюун), also transcribed S. Oyun, is a Mongolian politician and geologist. She is the leader of the Civil Will Party, is the former Minister of Environment and Green Development, and has been a Member of Parliament of Mongolia (State Great Khural) since 1998. She is also a former Minister of Foreign Affairs and is the current head of the Zorig Foundation. Now she is new head of Global Water Partnership GWP. In 2003, Eisenhower Fellowships awarded Oyun a fellowship program in the United States. In 2006, Oyun was selected as a Young Global Leader (YGL) by the Davos World Economic Forum (WEF). She has been an active member of the YGL community since. On June 24, 2014, Oyun was elected the first president of the United Nations Environment Assembly (U