Charles (Italian Carlo) of Sezze (baptismal name Giancarlo Marchioni) was born on October 22, 1613 at Sezze in the Papal States to an Italian peasant family. At the age of 22 (1635), Charles entered the Franciscan Order at the Convent of Nazzano as a lay-brother.
Charles spent the 35 years (1635–1670) as a Franciscan lay-brother — serving as cook, porter, infirmarian, sacristan at multiple Roman Franciscan convents.
Charles became famous during his lifetime for his mystical-ecstatic experiences and his hidden-humility Franciscan vocation. In 1648, Charles received the mystical experience of the wounding of the heart by the Eucharistic Christ during the Mass — the wound producing a physical mark that became visible after his death.
Charles became the personal spiritual director of Pope Clement IX (1667–1669) — the relationship that established his Roman Franciscan-mystical reputation.
He composed his Autobiography (Le Grandezze delle Misericordie di Dio, 'The Greatnesses of the Mercies of God') — one of the principal 17th-century Italian Franciscan mystical-literary works.
He died at Rome on January 6, 1670 at the age of 56. Canonized on April 12, 1959 by Pope St. John XXIII.