Nicholas deBelleville Katzenbach (January 17, 1922 – May 8, 2012) was an American lawyer who served as United States Attorney General during the Lyndon B. Johnson administration.

He was named after his mother's great-great-grandfather, Nicolas de Belleville (1753–1831), a French medical doctor who accompanied Kazimierz Pułaski to America and settled in Trenton in 1778.

Katzenbach was a junior at Princeton in 1941 who enlisted in the U.S. Armed Forces right after Pearl Harbor and served in the United States Army Air Corps in World War II.

He spent over two years as a prisoner of war in Italian and German POW camps, including Stalag Luft III, the site of the "Great Escape", in which Katzenbach assisted.

On February 11, 1965 President Johnson appointed Katzenbach the 65th Attorney General of the United States, and he held the office until October 2, 1966.

While Under Secretary of State, he commented on the 1967 USS Liberty incident: “There was nobody I think who did not believe that the Israelis knew it was an American ship that they were attacking.”[12] In September 2008, Katzenbach published Some of It Was Fun: Working with RFK and LBJ (W. W. Norton), a memoir of his years in Government service.

[15] On November 25, 1963, he sent a memo to Johnson's White House aide Bill Moyers recommending the creation of a Presidential Commission to investigate the assassination.

[16] Four days after Katzenbach's memo, Johnson appointed some of the nation's most prominent figures, including the Chief Justice of the United States, to the Commission.

[15][16] Conspiracy theorists later called the memo, one of thousands of files released by the National Archives in 1994, the first sign of a cover-up by the government.

He and Cravath, Swaine & Moore attorney Thomas Barr led the case for the computer giant for 13 years until the government finally decided to drop it in 1982.

[23] Katzenbach and his wife Lydia retired to the Princeton, New Jersey area, with a summer home in West Tisbury, Massachusetts on Martha's Vineyard.