Humanum genus is a papal encyclical promulgated on 20 April 1884 by Pope Leo XIII.

Released in the ascent of the industrial age, Marxism, and the aftermath of the September 20, 1870, Capture of Rome by the Kingdom of Italy military forces from the Papal States, Humanum genus is principally a condemnation of Freemasonry. It states that the late 19th century was a dangerous era for the Roman Catholic Church, largely due to numerous concepts and practices it attributes to Freemasonry, namely naturalism, popular sovereignty, and the separation of church and state.

Some of the strictures found in Humanum genus still remain in force today.

Pope Leo XIII (Italian: Leone XIII; born Vincenzo Gioacchino Raffaele Luigi Pecci; 2 March 1810 – 20 July 1903) was the head of the Catholic Church from 20 February 1878 to his death in 1903. Living until the age of 93, he was the oldest pope (with the exception of Pope Benedict XVI as emeritus pope), and had the third-longest confirmed pontificate, behind those of Pius IX (his immediate predecessor) and John Paul II.

He is well known for his intellectualism and his attempts to define the position of the Catholic Church with regard to modern thinking. In his famous 1891 encyclical Rerum novarum, Pope Leo outlined the rights of workers to a fair wage, safe working conditions, and the formation of trade unions, while affirming the rights of property and free enterprise, opposing both socialism and laissez-faire capitalism. With that encyclical, he became popularly titled as the "Social Pope" and the "Pope of the Workers", also having created the foundations for modern thinking in the church's social doctrine, influencing the thoughts of his successors. He influenced Mariology of the Catholic Church and promoted both the rosary and the scapular. Upon his election, he immediately sought to revive Thomism, the theology of Thomas Aquinas, desiring to refer to it as the official theological and philosophical foundation for the Catholic Church. As a result, he sponsored the Editio Leonina in 1879.

Leo XIII is particularly remembered for his belief that pastoral activity in the socio-political field was also a vital mission of the church as a vehicle of social justice and maintaining the rights and dignities of the human person.

Leo XIII issued a record of eleven papal encyclicals on the rosary, earning him the title of the "Rosary Pope". In addition, he approved two new Marian scapulars and was the first pope to fully embrace the concept of Mary as Mediatrix. He was the first pope never to have held any control over the Papal States, which had been dissolved by 1870. Similarly, many of his policies were oriented towards mitigating the loss of the Papal States in an attempt to overcome the loss of temporal power, but nonetheless continuing the Roman Question.

At his death in 1903 he was briefly buried in the grottos of Saint Peter's Basilica before his remains were later transferred in 1924 to the Basilica of Saint John Lateran.