Costanzo I of Sforza (July 1447 – 4 July 1483) was an Italian condottiero, lord of Pesaro and Gradara. He was the son of Alessandro Sforza, under whom he fought in his early years and from whom he inherited the lordship of Pesaro. He also received the lordship of Gradara from Pope Alexander VI. He fought for various Italian states of the time, including the Kingdom of Naples and the Papal States. His illegitimate son Giovanni succeeded him in Pesaro.