The world leader famous for his doctrine of non-interventionism during the 1930s was Franklin D. Roosevelt. His approach to foreign policy emphasized avoiding direct conflict in international affairs, particularly before the U.S. entered World War II. Roosevelt's administration focused on the Good Neighbor Policy towards Latin America and advocated for neutrality in European conflicts. This period set the stage for shifting American foreign policy and reflected the isolationist sentiments prevalent in the U.S. at the time.