William Harding Jackson (March 25, 1901 – September 28, 1971) was a U.S. civilian administrator, New York lawyer, and investment banker who served as Deputy Director of the Central Intelligence Agency.

Following the stock market crash of 1929, Jackson moved to the business and financial interest law firm of Carter, Ledyard & Milburn, where he became a full partner in 1934.

Jackson was the principal author (along with investment banker Alexander Standish and Harold B. Ingersoll) of the USAAF Bay of Biscay Intelligence Estimate, calling for the attack on Nazi U-boats at their source on the coast of France.

After graduation from Harrisburg in June 1942, Jackson was promoted to Major and brought into the War Department by Secretary Henry L. Stimson, where he became General Staff (Chief of Secret Intelligence reporting to General George C. Marshall from the European Theater of Operations (ETO) at COSSAC headquarters) with the cover title Chief of G-2 intelligence for First Army Group (FUSAG).

After training on the Enigma codes at Bletchley Park, UK, he became the senior ULTRA Special Counter-Intelligence Units (SCIU) team leader for all US armies in the ETO.

By summer of 1943, he was given the 'cover title' Assistant Attache for Air, stationed at the US Embassy under Ambassador Gil Winant near Grosvenor Square, next to the Office of Strategic Services (OSS).

Shortly thereafter he was promoted to full colonel and appointed G-2 intelligence chief at FUSAG headquarters in London's West End to work on Operation Bodyguard, the massive deception plan to make the Nazis believe the D-Day assault (Operation Overlord) would come from Scandinavia in the north and at Pas-de-Calais under the command of Gen. George S. Patton, at the narrowest point of the English Channel.

After the successful D-Day feint, Jackson was made head of all OSS X-2 Special Counter-Intelligence Units (SCIU) in the ETO, traveling with Twelfth Army Group's forward EAGLE TAC headquarters to Luxembourg on General Omar Bradley's staff.

[7] Decorations—For service to his country and the people of Europe, Jackson was awarded the Bronze Star Medal, the Legion of Merit with one Oak Leaf Cluster (OLC), and the Belgian Croix de Guerre.

[2] On July 18, 1950, the new Secretary of Defense, Louis Johnson, and General Omar Bradley sent a letter to President Truman nominating William Harding Jackson for Director of Central Intelligence to replace Hillenkoetter.

When Jackson declined because of philanthropic and business commitments in New York, Truman is said to have all but issued a direct order as commander-in-chief to General Smith, that he would become the next DCI.

He was the first Deputy Director of Central Intelligence (DDCI) to serve under Walter Bedell Smith (DCI), former Ambassador to the Soviet Union (1945–46) and former World War II four-star General.

During the Eisenhower Administration, Bill Jackson is listed by the 'White House Staff' publication[11] and by the CIA as being a 'Special Adviser' and 'Senior Consultant to the Director of Central Intelligence' (from 1951–1955).

While employed as managing director at J. H. Whitney & Co., Jackson was named 'Special Assistant to the Secretary of State' John Foster Dulles to attend the 1955 Big Four talks in Geneva.

President Eisenhower appointed Jackson to additional responsibilities serving as Acting United States National Security Advisor from September 1, 1956, until January 7, 1957.