The Italian moviemaker worked on more than 100 scripts and was best known for his regular collaboration with director Michelangelo Antonioni, earning an Oscar nomination for best screenplay for their film Blow-Up in 1967.
He was also nominated for an Academy Award for 1973 movie Amarcord, with fellow writer Federico Fellini, and in 1966 for Casanova 70.
Guerra was born in 1920, and honed his writing skills after he was imprisoned in a German concentration camp during World War II.
He was part of the famed neo-realism movement in Italian cinema during the late 1940s and '50s, but later worked with contemporary directors including Steven Soderbergh and Giuseppe Tornatore.
Italy's former culture minister Walter Veltroni said, "We have lost a poet, a genius and marvellous person."
Guerra was honoured with a lifetime achievement award at the Venice Film Festival in 1994.