Oum Sang-il is a Korean mathematician working in graph theory and discrete mathematics. He is a tenured professor in the Department of Mathematical Sciences at KAIST and the chief investigator of the Discrete Mathematics Group in the Pioneer Research Center for Mathematical and Computational Sciences at the Institute for Basic Science. He is known for his work on structural graph theory and in particular for structures and algorithms relating to rank-width, clique-width, and branch-width. He published more than 45 journal papers. He won the Young Scientist Award from the SouthKorean government in 2012. and the TJ Park Young Professor Fellowship from the POSCO TJ Park Foundation in 2009. He has been an editor of the Journal of the Korean Mathematical Society since 2011 and a founding member of Young Korean Academy of Science and Technology. He wrote a monthly pieces for the monthly magazine "Math Donga" :ko:%EC%88%98%ED%95%99%EB%8F%99%EC%95%84| for 4 years from 2016, sharing the latest research breakthroughs in mathematics. In the Korean Mathematical Society :ko:%EB%8C%80%ED%95%9C%EC%88%98%ED%95%99%ED%9A%8C|, he was appointed twice as an executive member of the board of trustees in charge of the Korean Mathematical Olympiad. He was a member of the Korean Mathematical Olympiad Committee for 2011-2018 and was the deputy leader of the South Korean team at the International Mathematical Olympiad in 2012 and 2018.
From 1999 to 2002, Oum worked as a computer programmer in Korea. He was a visiting assistant professor in the School of Mathematics, Georgia Tech for 2005-2006 and a postdoctoral fellow under Jim Geelen in the Department of Combinatorics & Optimization in the University of Waterloo in 2007. In 2008, he joined the Department of Mathematical Sciences KAIST as an assistant professor before coming an associate professor and then full professor in 2011 and 2016, respectively. He was an affiliate professor in the School of Mathematics, Korea Institute for Advanced Study for several years. In 2018, he was appointed as the CI of the Discrete Mathematics Group in the Pioneer Research Center for Mathematical and Computational Sciences at the Institute for Basic Science. This and the Pioneer Research Center for Biomolecular and Cellular Structure are the first of two such centers at IBS.