Guadagni is a surname. Notable people with the surname include:
Bernardo Guadagni (1361–1434), Gonfalonier of Justice Gaetano Guadagni (1728–1792), Italian mezzo-soprano castrato singer Giovanni Antonio Guadagni (1674–1759), Italian Roman Catholic cardinal Nicky Guadagni (born 1952), Canadian actress
See also Guadagnino, surname Guadagno, surname Palazzo Guadagni Strozzi Sacrati, palace in Tuscany