Collins Jacques Seitz (June 20, 1914 – October 16, 1998) was a United States circuit judge of the United States Court of Appeals for the Third Circuit.

Born on June 20, 1914, in Wilmington, Delaware, Seitz received an Artium Baccalaureus degree in 1937 from the University of Delaware and a Bachelor of Laws in 1940 from the University of Virginia School of Law. He entered private practice in Wilmington from 1940 to 1946. He served as a Vice Chancellor of the Delaware Court of Chancery from 1946 to 1951, as a justice of the Delaware Supreme Court from 1949 to 1951, and as the Chancellor of the Delaware Court of Chancery from 1951 to 1966.^[1]

Seitz was nominated by President Lyndon B. Johnson on February 28, 1966, to a seat on the United States Court of Appeals for the Third Circuit vacated by Judge John Biggs Jr. He was confirmed by the United States Senate on June 9, 1966, and received his commission on the same day. He served as Chief Judge from 1971 to 1984. He was a member of the Judicial Conference of the United States from 1971 to 1984. He assumed senior status on June 1, 1989. His service terminated on October 16, 1998, due to his death in Wilmington.^[1]

Seitz's daughter, Virginia A. Seitz, is a well-known attorney, formerly at the Office of Legal Counsel of the United States Department of Justice, and now at Sidley Austin. Seitz's son, Collins J. Seitz Jr., is the chief justice of the Delaware Supreme Court. C.J. Seitz was a founding partner at the Delaware law firm of Seitz Ross Aronstam & Moritz.^[5] A brother, John F. R. Seitz, was a career United States Army officer who served as a colonel in World War II and retired at the grade of major general.^{[citation needed]}