Fernando Di Leo was an Italian film director and script writer born in San Ferdinando di Puglia. During his career from 1964 to 1985, Di Leo directed 20 films and was involved in the writing process in 43. His films influenced many popular contemporary directors, such as Quentin Tarantino and John Woo.
Di Leo started his career mostly writing scripts for spaghetti westerns. He worked on the script for Per un pugno di dollari and later as assistant director and assistant to Sergio Leone in Per qualche dollaro in più. Later, he wrote scripts for such westerns as Navajo Joe and Johnny Yuma. Di Leo is now best remembered for his poliziotteschi films, especially the Milieu Trilogy, which he both wrote and directed. The trilogy contains Milano calibro 9, La mala ordina and Il boss.