Mario Rafael Díaz-Balart Caballero (/bəˈlɑːrt/; born September 25, 1961) is an American politician serving as the U.S. representative for Florida's 25th congressional district. A Republican, he was elected in 2002, and his district includes much of southwestern Miami-Dade County, including Hialeah, and much of the northern portion of the Everglades. Díaz-Balart was the first member of Congress to test positive for COVID-19 on March 18, 2020. After Representative Alcee Hastings's death in April 2021, Díaz-Balart became the dean (or longest-serving member) of Florida's congressional delegation.