Konrad Kellen (born Konrad Moritz Adolf Katzenellenbogen; December 14, 1913 – April 8, 2007) was a German-born American political scientist, intelligence analyst and author.
At different points in his career, Kellen analyzed postwar German soldiers, defectors from behind the Iron Curtain, captured Viet Cong, and terrorists. He was among the first intelligence analysts to conclude that, contrary to prevailing U.S. administration assessments, enemy morale in the Vietnam War was in fact high and that the war was not winnable; while at the RAND Corporation Kellen co-authored an open letter to the U.S. government urging withdrawal of troops.