1898
Pope Leo XIII publishes four Papal Encyclicals, Caritatis Studium, addressed to the Scottish Bishops; Spesse Volto, about Catholic Action in Italy; Diuturni Temporis, on the Rosary; and Quum Diuturnum, convoking the Latin-American Bishops to Rome.

The Holy Shroud of Turin was solemnly exposed. Permission was granted to photograph the Sacred Relic and a sensation was caused by the discovery that the image upon the linen was apparently a negative! In other words, the photographic negative taken from the Shroud offered a more recognizable picture of a human face than the cloth itself or any positive print! In the photographic negative the lights and shadows were natural, in the linen or the print they were inverted. The photographer to first capture the image of the Holy Shroud on film was Secundo Pia.

1899
Pope Leo XIII only published two Papal Encyclicals, Depuis Le Jour, on clerical education in France; and Paternae, on Ecclesiastical education in Brazil.

Pope Leo XIII names St. Bede the Venerable, Doctor of the Church.

On May 25, Pope Leo XIII dedicated the world to the Sacred Heart of Jesus, as Prince and Lord of all, Catholics and non-Catholics, Christians and non-Christians.

The Pontiff, in an Apostolic letter to Cardinal Gibbons, he condemns Americanism. This movement claimed that the Church should adjust its doctrines, especially in morality, to the culture of the people; emphasizing the active virtues of social welfare and democratic equality, it underrated the passive virtues of humility and obedience to ecclesiastical authority.

Pope Leo XIII held the first Plenary Council of Latin America in Rome.

Pope Leo XIII answered the question on when does the new Century begin. The Pontiff explained that a century is a period of 100 years and since there is no year zero, it begins with "one" and ends with the "hundred mark."

1899-1900
The Boxer Rebellion. Many Catholics suffered martyrdom during this revolt in China. A secret society od Chinese, which westerners called the Boxers, began terrorizing Christian missionaries, mostly Catholics. In 1900 these attacks culminated in the violent Boxer Rebellion in Beijing, which claimed the lives of many Chinese and foreigners. The Western powers sent a relief expedition which occupied the city and ended the rebellion.

1900
Pope Leo XIII celebrates the Holy Year Jubilee.

Pope Leo XIII publishes two more Papal Encyclicals, Omnibus Compertum, on the union among Greek Melchites; and Tametsi, on Jesus Christ our Redeemer.

The early Pentecostal churches begin to form.