Charles of Sezze - born Giancarlo Marchioni - was an Italian professed religious from the Order of Friars Minor. He became a religious despite the opposition of his parents who wanted him to become a priest and he led an austere life doing menial tasks such as acting as a porter and gardener; he was also a noted writer. He was also held in high esteem across the Lazio region with noble families like the Colonna and Orsini praising him and seeking his counsel as did popes such as Innocent X and Clement IX.

The Order of Friars Minor is a mendicant Catholic religious order, founded in 1209 by Francis of Assisi. The order adheres to the teachings and spiritual disciplines of the founder and of his main associates and followers, such as Clare of Assisi, Anthony of Padua, and Elizabeth of Hungary, among many others. The Order of Friars Minor is the largest of the contemporary First Orders within the Franciscan movement.