Italian painter, active mostly in Rome, and known principally for his paintings executed in a Late Baroque Classical manner. Although he is part of the classical tradition stemming from Raphael, he was not exempt from the influence of Baroque painting and particularly in his use of colour. He went to Rome in 1636, where he became an apprentice in the studio of Andrea Sacchi. He developed a close relationship with Sacchi till the death of his master in 1661. His fresco of "Constantine ordering the Destruction of Pagan Idols" (1648) for the Baptistery of the Lateran, based on designs by Sacchi, gained him attention as an artist but his first prominent independent work was the "Adoration of the Shepherds" (1650) for San Giuseppe di Falegnami. Another major work from this period was "The Mystery of the Trinity Revealed to St. Augustine" (c. 1655) painted for the church of Santa Maria dei Sette Dolori. Pope Alexander VII (reigned 1655–1667) commissioned many paintings from him including "The Visitation" (1656) for Santa Maria della Pace and the "Nativity" in the gallery of the Quirinal Palace where he worked under the direction of Cortona who selected him for this task, and during the 1670s he was commissioned by Pope Clement X to fresco the ceiling of the salone in the Palazzo Altieri; the iconographic programme for "The Triumph of Clemency" was devised by Bellori. His major works of this period included: "The Appearance of the Virgin to St. Philip Neri" (c. 1675) now in the Pitti Palace in Florence; "The Virgin with Saints Carlo Borromeo and Ignatius of Loyola, and Angels" (c. 1685) for the church of Santa Maria in Vallicella (c. 1675); and "The Assumption of the Virgin with Doctors of the Church" (1689) for Santa Maria del Popolo.