Charles of Sezze (19 October 1613 – 6 January 1670) - born Giancarlo Marchioni - was an Italian professed religious from the Order of Friars Minor.

[1] 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.

[4] His mother - when he was a toddler - liked to dress him in a dark tunic with a cord and hood in honor of friars Francis of Assisi and Anthony of Padua and she kept this 'habit' even after he outgrew it.

[3][1] He made a private vow to remain chaste in 1630 and in 1633 fell ill to the point of near death that he pledged to join the Order of Friars Minor if he were to be healed of his ailment.

[2] His parents encouraged his call to become a priest, though he was a poor student and largely illiterate, leaving seldom hope of his excelling in advanced studies.

He felt a desire to serve in the missions in India and later became inspired from the lives of Pascal Baylon and Salvador of Horta - who were both professed religious.

He made his solemn profession into the order on 19 May 1636 into the hands of Father Angelo Maria and his religious name was "Cosmas" at first but his mother's insistence saw it changed to "Carlo".

On 6 January 1670, he died in the convent attached to San Francesco a Ripa in Rome; he was buried in that church, where a chapel dedicates to his name still hosts his remnants.