Pope Gregory XIII, born Ugo Boncompagni, was head of the Catholic Church and ruler of the Papal States from 13 May 1572 to his death in April 1585. He is best known for commissioning and being the namesake for the Gregorian calendar, which remains the internationally accepted civil calendar to this day.

The Discalced Carmelites, known officially as the Order of the Discalced Brothers of the Blessed Virgin Mary of Mount Carmel or the Order of Discalced Carmelites, is a Catholic mendicant order with roots in the eremitic tradition of the Desert Fathers. The order was established in the 16th century, pursuant to the reform of the Carmelite Order by two Spanish saints, Teresa of Ávila (foundress) and John of the Cross (co-founder). Discalced is derived from Latin, meaning "without shoes".