John Helm Pratt (November 17, 1910 – August 11, 1995) was an American lawyer and judge. Born in New Hampshire, Pratt spent most of his life in the Washington, D.C. area, where he practiced law for 34 years before being appointed as a United States district judge of the United States District Court for the District of Columbia in 1968 by President Lyndon B. Johnson. As a federal judge, Pratt presided over a number of significant cases, including the Watergate trial of G. Gordon Liddy and civil rights cases involving school desegregation and discrimination based on sexual orientation.