John Helm Pratt (November 17, 1910, Portsmouth, New Hampshire-August 11, 1995, Chevy Chase, Maryland, was an American judge.
He was educated at Harvard University, graduating A.B. in 1930, and at Harvard Law School (LL.B., 1934). He was in private legal practice in Washington, DC, 1934-1942. He served in the U.S. Marines as Captain, 1942–1946, returning to private practice in Washington, 1946-1968.
He was nominated by Lyndon B. Johnson on April 11, 1968, to a seat vacated by Alexander Holtzoff, on the U. S. District Court for the District of Columbia. He was confirmed by the United States Senate on June 6, 1968, and received his commission on June 7, 1968. He assumed senior status on December 1, 1989. Service terminated at his death on August 11, 1995.