Costante Girardengo (Italian pronunciation: [koˈstante dʒirarˈdeŋɡo; -ɛŋɡo]; 18 March 1893 - 9 February 1978) was an Italian professional road bicycle racer, considered by many to be one of the finest riders in the history of the sport. He was the first rider to be declared a "Campionissimo" or "champion of champions" by the Italian media and fans. At the height of his popularity in the 1920s he was said to be more popular than Mussolini and it was decreed that all express trains should stop in his home town Novi Ligure, an honour only normally awarded to heads of state.

Stadio Costante Girardengo is a football stadium located in Novi Ligure, Italy. It is the home to the Novese, currently competing in Serie D. It opened in 1966 and holds 3,500 spectators.

Costante Adolfo Bossi (1876 – 1953) was an Italian organist, composer and teacher. He was the brother of Marco Enrico Bossi and son of Pietro Bossi.

Costante Degan (March 12, 1930 – July 1, 1988) was an Italian Christian Democrat politician. He was minister of health (1983–1986) in the Government of Italy. He served in the cabinet of Prime Minister Bettino Craxi. He was Mayor of Venice (1988). He served in the Chamber of Deputies of Italy in Legislature IV (1963–1968), Legislature V (1968–1972), Legislature VI (1972-1976), Legislature VII (1976–1979) and Legislature VIII (1979–1983). He served in the Senate of Italy in Legislature IX (1983–1987) and Legislature X (1987-1992).

Orazio Costante Grossoni (Milan, 1867–1952) was an Italian sculptor.

Costante Lussana (4 February 1892 – 29 September 1944) was an Italian long-distance runner who competed at the 1920 Summer Olympics,