William J. Brennan, Jr., American colonel and Associate Justice of the United States Supreme Court (d. 1997)
William Joseph Brennan Jr. (April 25, 1906 – July 24, 1997) was an American lawyer and jurist who served as an Associate Justice of the United States Supreme Court from 1956 to 1990. He was the seventh-longest-serving justice in Supreme Court history, and known for being a leader of the Court's liberal wing.Born in Newark, New Jersey, Brennan studied economics at the University of Pennsylvania, then attended Harvard Law School. He entered private legal practice in New Jersey and served in the U.S. Army during World War II. He was appointed in 1951 to the Supreme Court of New Jersey. Shortly before the 1956 presidential election, President Dwight D. Eisenhower used a recess appointment to place Brennan on the Supreme Court. Brennan won Senate confirmation the following year. He remained on the Court until his retirement in 1990, and was succeeded by David Souter.

On the Supreme Court, Brennan was known for his outspoken progressive views, including opposition to the death penalty and support for abortion rights and gay rights. He authored several landmark case opinions, including Baker v. Carr (1962), establishing that the apportionment of legislative districts is a justiciable issue, Eisenstadt v. Baird, which made contraception available to unmarried people, and helped solidify the sexual revolution, and New York Times Co. v. Sullivan (1964), which required "actual malice" in libel suits brought by public officials.

Due to his ability to shape a variety of wide opinions and "bargain" for votes in many cases, he was considered to be among the Court's most influential members. Justice Antonin Scalia called Brennan "probably the most influential Justice of the [20th] century."