A puisne judge or puisne justice (//; French: puisné or puîné, "junior") is a regular member of a court other than the court's chief judge or chief justice, or any ex officio member of the court (e.g. the Chancellor of the High Court with respect to the Court of Appeal of England and Wales).
The term is used almost exclusively in common law jurisdictions such as the jurisdiction of England and Wales within the United Kingdom, Australia, including its states and territories; Canada, including its provinces and territories; India and its constituent states; the British possession of Gibraltar; Kenya; Sri Lanka; and Hong Kong.
The term puisne judge/justice is not used by the United States, notwithstanding its being a common law jurisdiction; nor by any of its 56 constituent states, territories or federal district - 51 of which are common law jurisdictions, and 3 of which are quasi-common law jurisdictions. Instead, the term associate justice is used by the United States Supreme Court, the DC Court of Appeal, and by most state and territorial high courts. The term associate judge is also used throughout the United States, but this frequently means something different from puisne or associate justice.
- Hong Kong remains a common law jurisdiction under the principle of "One Country, Two Systems" enacted prior to the repatriation of the former British Crown Colony in 1997.
- Louisiana and Puerto Rico are civil law jurisdictions; American Samoa and the Northern Mariana Islands use a mix of local customary law and common law; and under 1 VIC Sec. 4, the basic law of the U.S. Virgin Islands is "The rules of the common law, as expressed in the Restatements of Law approved by American Law Institute, and to the extent not so expressed, as generally understood and applied in the United States ... in the absence of local laws to the contrary."
- 28 U.S. Code § 1.