Jack Greenberg (December 22, 1924 – October 12, 2016) was an American attorney and legal scholar. He was the Director-Counsel of the NAACP Legal Defense Fund from 1961 to 1984, succeeding Thurgood Marshall. He was involved in numerous crucial cases, including Brown v. Board of Education, which ended segregation in public schools. In all, he argued 40 civil rights cases before the U.S. Supreme Court, and won almost all of them.

He was Alphonse Fletcher Jr. Professor of Law Emeritus at Columbia Law School, and had previously served as dean of Columbia College and vice dean of Columbia Law School. He died on October 12, 2016.

Greenberg was born into a Jewish family in Brooklyn, New York on December 22, 1924. His brother was science journalist Daniel S. Greenberg.

During World War II, Greenberg served in the United States Navy and fought at Okinawa and Iwo Jima. Greenberg commanded a landing craft in the invasion of Iheya Jima, one of the final campaigns of the war. During his service, he was disturbed by racial prejudice he perceived in the Navy, and was threatened with a court martial for shouting at a superior officer in defense of a black crewman that he felt was being mistreated.

After an interruption due to his war service Greenberg graduated from Columbia College with a B.A. in 1945. He further received an LL.B. from Columbia Law School in 1948, and an LL.D. (an honorary degree) from Columbia Law in 1984.

Greenberg became the only white legal counselor for the NAACP Legal Defense and Educational Fund ("LDF") in 1949, and, in 1961, succeeded Thurgood Marshall as LDF's Director-Counsel.

Greenberg recalled his earliest arguments before the Supreme Court, saying:

It was like a religious experience; the first few times I was there I was full of awe. I had an almost tactile feeling. The first time I was in the Court, I wasn't arguing. I felt as if I were in a synagogue, and reached to see whether or not I had a yarmulke on. I thought I ought to have one on.