Summorum Pontificum (English: Of the Supreme Pontiffs) is an Apostolic Letter of Pope Benedict XVI, issued motu proprio (i.e., on his own initiative), by which he specified the circumstances in which priests of the Latin Church may celebrate Mass according to what he called the "Missal promulgated by Blessed John XXIII in 1962" (the latest edition of the Roman Missal in the form known as the Tridentine Mass or Traditional Latin Mass), and administer most of the sacraments in the form used before the liturgical reforms that followed the Second Vatican Council.