Louis O'Melville "Lou" Frost, Jr. (September 19, 1931 – January 16, 2008) was an American lawyer who served for 36 years as the elected public defender for Florida's Fourth Judicial Circuit, which consists of Duval, Nassau, and Clay counties. He was a local legal institution who nurtured the careers of hundreds of young lawyers, with two dozen appointed to state and federal judgeships, and one seated on the Florida Supreme Court.