He was 90.
Along with pressing for civil rights legislation, Katzenbach, who died Tuesday night, played big roles in major events of the 1960s, The New York Times reported.
He confronted then-Alabama Gov. George Wallace at the University of Alabama in 1963 after the governor vowed to prevent to black students from entering. Katzenbach told the governor, "I'm not interested in this show" and later escorted the two students to register.
Katzenbach advised John F. Kennedy during the Cuban missile crisis and negotiated the release of Cuban prisoners captured during the Bay of Pigs invasion. He went to Johnson to protest FBI Director J. Edgar Hoover's bugging hotel rooms to record civil rights leader Martin Luther King's extramarital sexual encounters, then trying to blackmail him.
Serving as an under-secretary of state, Katzenbach defended before Congress Johnson's escalation of the war in Vietnam.
"Few men have been so deeply involved in the critical issues of our time," Johnson wrote to him when Katzenbach left government in 1968.
Katzenbach lobbied Republican senators in 1964 to help pass the Civil Rights Act of 1964 and the Voting Rights Act of 1965, which he helped draft, and he defended the Civil Rights Act before the Supreme Court.
Katzenbach left government after Richard M. Nixon was elected president and joined IBM as senior vice president and general counsel.
Katzenbach resigned from IBM in 1986 and went into private practice at a New Jersey law firm.
He had enlisted in the Army Air Forces after the Pearl Harbor attack and was captured after his plane was shot down on a mission in 1943. While a prisoner of war in Germany for 15 months, he said he read 400 books.
Katzenbach convinced Princeton University his reading qualified him for an undergraduate degree and he graduated cum laude in 1945 after taking nine exams and writing a thesis. He graduated from Yale Law School and studied at Balliol College at Oxford on a Rhodes scholarship.