Lawrence Giustiniani was a 15th-century Venetian prelate, theologian, and philosopher. Born in Venice in 1381, he joined the Canons Regular of Saint Augustine at San Giorgio in Alga in 1404. After serving as the first prior of his Augustinian community and later as Prior General, he was appointed Bishop of Castello in 1433. He eventually became the first Patriarch of Venice in 1451, providing counsel to the city during the fall of Constantinople. He died in Venice on January 8, 1456.