Julian William Mack (July 19, 1866 – September 5, 1943) was a United States circuit judge of the United States Commerce Court, the United States Court of Appeals for the Seventh Circuit, the United States Circuit Courts for the Seventh Circuit, the United States Court of Appeals for the Second Circuit and the United States Court of Appeals for the Sixth Circuit.

Mack was born on July 19, 1866, in San Francisco, California,^[1] the son of William Jacob and Rebecca (Tandler) Mack.^[2] His father, who came from Bavaria in about 1849, was a Jewish merchant, engaged in business successively in Cincinnati, Ohio, Terre Haute, Indiana, San Francisco, California, and again in Cincinnati.^[2] Mack received his early education in the public schools of Cincinnati,^[2] then received a Bachelor of Laws in 1887 from Harvard Law School.^[1] He graduated at the top of his class, and was selected as the class orator for graduation in 1887.^[2] Encouraged by Harvard law professors, Mack and several of his classmates founded the Harvard Law Review.^[2] He served as its first business manager and as a member of the editorial board.^[2] He received a Parker Fellowship from Harvard University and attended the Humboldt University of Berlin and the University of Leipzig in the German Empire from 1887 to 1890.^[1] He entered private practice in Chicago, Illinois, from 1890 to 1895.^[1] He was a Professor of Law for Northwestern University from 1895 to 1902.^[1] He was a Professor of Law for the University of Chicago from 1902 to 1911.^[1] He was a Judge of the Illinois Circuit Court for Cook County, Illinois, from 1904 to 1905.^[1] He was a Judge of the Illinois Appellate Court from 1905 to 1911.^[1]

Mack was an active participant in many of the social reform movements which emerged in Chicago and the nation during the 1890s and early twentieth century.^[2] Mack worked at Hull House and taught social workers at the Chicago School of Civics and Philanthropy, and later became President of the National Conference of Charities and Corrections.^[2] In 1904, he became President of the National Conference of Social Workers.^[2] He helped organize the Juvenile Protective League, forerunner of the Child Welfare League of America, and lobbied on behalf of protective legislation for minors and immigrant rights.^[2] He was an early supporter of the National Association for the Advancement of Colored People and the American Civil Liberties Union.^[2] He served as secretary of the United Jewish Charities, the association responsible for overseeing and funding Chicago Jewish philanthropic activities.^[2]

Mack was nominated by President William Howard Taft on December 12, 1910, to the United States Commerce Court, the United States Court of Appeals for the Seventh Circuit and the United States Circuit Courts for the Seventh Circuit, to a new joint seat authorized by 36 Stat. 539.^[1] He was confirmed by the United States Senate on January 31, 1911, and received his commission the same day.^[1] On December 31, 1911, the Circuit Courts were abolished and he thereafter served on the Commerce Court and Court of Appeals.^[1] On December 13, 1913, the Commerce Court was abolished and he thereafter served only on the Court of Appeals.^[1] Mack was reassigned by operation of law to the United States Court of Appeals for the Sixth Circuit and the United States Court of Appeals for the Second Circuit on July 1, 1929, to a new joint seat authorized by 36 Stat. 539.^[1] On June 30, 1930, Mack was reassigned by operation of law to serve on the Second Circuit only, pursuant to the provisions of 36 Stat. 539.^[1] He assumed senior status on September 6, 1940.^[1] His service terminated on September 5, 1943, due to his death in New York City, New York.^[1]

Mack was a member of the United States War Department Board of Inquiry on Conscientious Objectors from 1918 to 1919.^[1][2]

Mack was President of the American Jewish Congress of 1918, the first American Jewish Congress.^[2] The permanent successor organization by the same name was founded in 1922.^[2]

Kibbutz Ramat HaShofet, founded in Israel in 1941, was named in his honour.^[4]

Mack was a member of Reform Judaism.^[2] His niece Eleanor married lawyer Max Lowenthal.^[5]

• List of Jewish American jurists