Puisne (from Old French puisne, modern putne, later born, inferior; Lat. postea, afterwards, and natus, born) is a term in law meaning " inferior in rank." It is pronounced "puny," and the word, so spelled, has become an ordinary adjective meaning weak or undersized.

The judges and barons of the common law courts at Westminster, other than those having a distinct title, were called puisne. By the Supreme Court of Judicature Act 1877 , a "puisne judge" is denned as a judge of the High Court other than the lord chancellor, the lord chief justice of England , the master of the rolls , the lord chief justice of the common pleas , and the lord chief baron , and their successors respectively.