Jack Bertrand Weinstein (August 10, 1921 – June 15, 2021) was a United States district judge of the United States District Court for the Eastern District of New York. Until his entry into inactive senior status on February 10, 2020, he maintained a full docket of cases.

Weinstein was born on August 10, 1921, into a Jewish family living temporarily in Wichita, Kansas. He was the son of Harry and Bessie (Brodach) Weinstein. He was raised partly in Brooklyn, New York. He graduated from Abraham Lincoln High School in Brooklyn's Brighton Beach district before receiving a Bachelor of Arts degree from Brooklyn College in 1943. During World War II, he served as a lieutenant in the United States Navy from 1943 to 1946. His duties included serving as deck officer on board the submarine USS Jallao, where he also ran the radar equipment. He graduated from Columbia Law School (on the G.I. Bill) with a Bachelor of Laws degree in 1948.

Weinstein continued to teach at his graduate alma mater as an untenured lecturer in law. In 1949, he completed a clerkship with New York State Court of Appeals Judge Stanley H. Fuld before opening his own law practice in Manhattan a year later—"in part because anti-Semitism at the time made finding work at a firm difficult." Following the recommendation of Columbia colleague Walter Gellhorn, Weinstein also worked with the NAACP Legal Defense Fund during this period; eventually, he was a member of the litigation team for Brown v. Board of Education (although he frequently downplayed his contributions, insisting that he was "doing the kind of work that a young associate would do: preparing briefs and research") before working on the "one man, one vote" litigation of the 1960s. His collaborators included such Columbia colleagues as Charles Black and Jack Greenberg. Weinstein also worked for Republican State Senator Seymour Halpern. While on the faculty of Columbia Law School, he concurrently served as county attorney of Nassau County, New York, from 1963 to 1965, overseeing "a large staff of attorneys who represented various county departments, including the police and social service agencies."

On January 16, 1967, he was nominated as a federal judge to the United States District Court for the Eastern District of New York, to a seat vacated by Judge Leo F. Rayfiel. He was confirmed by the United States Senate on April 14, 1967, and received his commission on April 15, 1967. He served as Chief Judge from 1980 to 1988.

As a federal judge, he worked with a number of mass tort cases, including those relating to Agent Orange, asbestos, tobacco, breast implants, diethylstilbestrol, Zyprexa, and handguns. He has been known to take on large numbers of cases from other judges, and on one occasion collected most of the unresolved habeas corpus petitions in the Eastern District to bring finality to the claims of many prisoners. Although Weinstein assumed senior status on March 1, 1993, he continued to maintain a full docket of cases until entering inactive senior status on February 10, 2020. His change to inactive senior status meant that while he remained a federal judge, he no longer heard cases or participated in the business of the court.

Following two years in private practice, Weinstein was appointed to a tenured professorship at Columbia Law School from 1952 (becoming a full professor in 1956) until commencing his judicial service in 1967. He was the first legal scholar appointed to Columbia Law School's tenure-track faculty after World War II and remained on the institution's faculty (likely nominally as an adjunct professor, although biographer Jeffrey B. Morris has maintained that Weinstein "was not just a part-time adjunct" because he continued to maintain a full courseload and professional relationships with his Columbia colleagues) until 1998.

From 1987 until his death, he was an adjunct professor at Brooklyn Law School.

The Second Circuit Appeals court reversed Weinstein's ruling in favor of the City of New York (Mayor Michael Bloomberg) against a group of gun manufacturers. The Second Circuit found the suit to be barred under Protection of Lawful Commerce in Arms Act (PLCAA). From the decision of April 30, 2008; "We conclude that the City's claim, predicated on New York Penal Law § 240.45, does not fall within an exception to the claim restricting provisions of the Act because that statute does not fall within the contours of the Act's predicate exception. We also hold that the PLCAA is a valid exercise of the powers granted to Congress pursuant to the Commerce Clause and that the PLCAA does not violate the doctrine of separation of powers or otherwise offend the Constitution in any manner alleged by the City."