Giustiniani, Orazio an Italian cardinal and theologian, was born at Genoa near the close of the 16th century. He was of that branch of the Giustiniani family to which the isle of Chios belonged. Having studied theology at Rome, he entered, at the age of twenty-five years, the congregation of priests of St. Philip of Neri, and advanced rapidly to the higher positions of his order. Urban VIII appointed him first librarian of the library of the Vatican. He was charged with an important negotiation with the patriarch of Constantinople. and acquitted himself so much to the satisfaction of the pope that he bestowed upon him as a reward the bishopric of Montalto, in 1640. He restored harmony between the bishops of Montalto and the inhabitants of that place. In 1645 Innocent X appointed him bishop of Nocera, and the year following he was made cardinal, with the title of St. Onuphrius. Soon after the pope chose him as his grand penitentiary. He became again first librarian of the Vatican library, and died at Rome in 1649. See Hoefer, Nouv. Biog. Generale, s.v.