Italian painter, head of the art department at the University of Notre Dame, 1874-1891. Born in Bologna, Gregori studied art there and in Palermo, Venice, and Florence. In 1840 he moved to Rome and worked in the Vatican restoring old paintings and creating new ones. In 1856 he won the gold medal of the Accademia Reale in Bologna for a large-scale historical painting.

In 1874 the Pope and members of the Curia recommended him to Father Edward Sorin for the job of head of the art department at Notre Dame. He came to Indiana and painted many frescoes in the buildings of the campus including a series of murals in the main building depicting episodes in the life of Christopher Columbus. He also painted portraits of many American bishops and of other figures of American history.