Robert Lansing (; October 17, 1864 – October 30, 1928) was an American lawyer and diplomat who served as Counselor to the State Department at the outbreak of World War I, and then as United States Secretary of State under President Woodrow Wilson from 1915 to 1920. A conservative pro-business Democrat, he was a strong advocate of democracy and of the United States' role in establishing international law. He was an avowed enemy of German autocracy and Russian Bolshevism. Before U.S. involvement in the war, Lansing vigorously advocated freedom of the seas and the rights of neutral nations. He later advocated U.S. participation in World War I, negotiated the Lansing–Ishii Agreement with Japan in 1917 and was a member of the American Commission to Negotiate Peace at Paris in 1919. However, Wilson made Colonel House his chief foreign policy advisor because Lansing privately opposed much of the Treaty of Versailles and was skeptical of the Wilsonian principle of self-determination.