Harold Hongju Koh (born December 8, 1954) is an American lawyer and legal scholar who served as the legal adviser of the Department of State in the Obama administration. He was nominated to this position by President Barack Obama on March 23, 2009, and confirmed by the Senate on June 25, 2009. He left the State Department in January 2013, returning to Yale University as a Sterling Professor of international law. He was elected to the American Philosophical Society in 2007.