William H. Hudnut III, who in his four terms as mayor of Indianapolis revitalized the city’s downtown with a focus on professional sports, died on Sunday in Chevy Chase, Md. He was 84. His death was confirmed by Dave Arland, a former aide and family spokesman, who said the cause was heart failure. Mr. Hudnut, a Republican, was elected mayor of Indianapolis in 1976, four years after he was elected to Congress. (He served one term in the House of Representatives but was defeated for re-election.) He would hold the office of mayor for 16 years, making him the longest-serving chief executive in the city’s history. Mr. Hudnut led efforts to bring the Baltimore Colts to Indianapolis, and the team relocated in time for the stadium’s completion in 1984. It was renamed the RCA Dome in 1994. Mr. Hudnut also expanded the city’s convention center and created the Indiana Sports Corporation, which has brought major sporting events to the city, including the 1982 National Sports Festival, the 1987 Pan-American Games and the 1991 World Gymnastics Championships. Today, Indianapolis is a center for gymnastics and home of the sport’s governing body. More than $4 billion was committed to urban development during Mr. Hudnut’s tenure as mayor. He left office in 1991 and moved to the Washington area. He was later elected to the town council in Chevy Chase and eventually served as the city’s mayor. He worked for several Washington think tanks and consulting firms, including the Urban Land Institute and the Bose Public Affairs Group, and served as an adviser to Georgetown University. He was also on the board of the National League of Cities. William Herbert Hudnut III was born on Oct. 17, 1932, in Cincinnati to William H. Hudnut Jr. and the former Elizabeth Allen Kilborne. Both his father and grandfather were Presbyterian ministers, and after graduating from Princeton University and Union Theological Seminary in New York, he was himself a Presbyterian minister in Annapolis, Md., Buffalo and Indianapolis before entering politics in 1972. Survivors include his wife, Beverly, and four sons, Timothy, William, Theodore and Christopher.