Harry A. Slattery (June 13, 1887 – September 1, 1949), was an American lawyer and politician. He was United States Under Secretary of the Interior from 1938 to 1939 and gave his name to the Slattery Report, which proposed to develop Alaska through immigration. The proposal, which included the settlement of Jewish refugees from Germany and Austria, largely in response to Nazi antisemitism, was never implemented.

He was born in Greenville, South Carolina. Slattery attended Mount Saint Mary's College in Maryland, Georgetown University and George Washington University.

In 1909–1912, he was secretary to Gifford Pinchot, Chief Forester in Theodore Roosevelt's administration.

In 1912–1917, he was Executive Secretary of the National Conservation Association, appointed by its founder, Pinchot.

In 1917–1918, he was Special Assistant to United States Secretary of the Interior Franklin K. Lane.

In 1919–1923, he was Counsel to the National Conservation Association. As part of government efforts to indict big business for the exploitation of the country's natural resources, he was involved in Senate investigations of the Mulhall exposure during Wilson's administration and the Teapot Dome Scandal of 1921.

In 1923–1933, he practiced law in Washington, D.C.

In 1925–1929, he was Executive and counsel for the National Boulder Dam Association. In 1929–1932, he Counsel for the National Conservation Commission. In 1931–1933, he was Washington, D.C. representative for the New York Power Authority. In 1933–1938, he was Personal Assistant to Harold Ickes, Secretary of the Interior, and Assistant to administrator of Federal Emergency Administration of Public Works.