Pope Leo XIII (2 March 1810 - 20 July 1903), born Vincenzo Gioacchino Raffaele Luigi Pecci to an Italian comital family, is the 256th Pope of the Roman Catholic Church, reigning from 1878 to 1903 in succession to Pope Pius IX.

Reigning until the age of 93, he is the oldest pope, and has the third longest pontificate, behind his immediate predecessor Pius IX and John Paul II.

He is known for intellectualism, the development of social teachings with his encyclical Rerum Novarum and his attempts to define the position of the Church with regard to modern thinking.

He impacts Roman Catholic Mariology and promotes both the rosary and the scapular.

He issues a record eleven encyclicals on the rosary, approves two new Marian scapulars and is the first Pope to fully embrace the concept of Mary as mediatrix.