The present, unpublished painting can be added to the five other known autograph portraits of Clement X executed by Baciccio. These include versions in the Palazzo Pitti, in the Galleria degli Uffizi, both Florence, and in the Marini collection, Rome (see F. Petrucci et al., in the exhibition catalogue, Giovanni Battista Gaulli. Il Baciccio, Ariccia, 1999-2000, pp. 113-5, nos. 11a and 11b).
Emilio Altieri, the future Clement X, was born in Rome on 13 July 1590 of a noble and pious family. Although he was a brilliant attorney, he entered the ranks of the clergy and rose to be bishop of Camerino in 1627. In 1647, he was sent by Innocent X as nunzio to Naples, where he encountered the aftermath of Masaniello's revolt against Spain. He fell into disfavor with Innocent and returned to his diocese. Alexander VII, however, recalled him to Rome, and Clement IX made him a cardinal on 27 November 1669. The following year, at the age of eighty, he was elected Pope Clement X. Despite his age, he was very active: he introduced social legislation to aid the poor and tried to improve agriculture and foster industry in the Papal States. He died on 22 July 1676.