Gennaro Maria Sarnelli, the son of the Baron of Ciorani, was born in Naples on September 12, 1702.
At the age of 14 following the beatification of Francis Regis he decided to become a Jesuit. Having been dissuaded by his father because of his youth he began the study of jurisprudence and took his Doctorate in ecclesiastical and civil law in 1722. He distinguished himself at the Bar and was enrolled in the Congregation of the Knights of the Legal and Medical Professions directed by the Pious Workers at St. Nicholas of Toledo. Among the rules of this Association there was the obligation of visiting the sick in the Hospital of the Incurables. It was here he heard the call of the Lord to become a priest.
In September 1728 he became a seminarian and was incardinated by Cardinal Pignatelli as a cleric in the parish of St. Anne di Palazzo. On June 4, 1729 in order to study in more peaceful conditions he became a boarder in the College of the Holy Family known as the Chinese College, founded by Matthew Ripa. On April 8 of the following year he left the Chinese College and on June 5 began his novitiate in the Congregation of the Apostolic Missions.
On May 28 1731 he concluded his novitiate and on July 8 of the following year he was raised to the Priesthood. During these years in addition to his visits to the hospital he devoted himself to helping young children forced to work and to teaching them the catechism. He also visited the old people in the Hospice of St. Gennaro and those condemned to the galleys who were ill in the hospital at the docks. These were also the years when he developed a friendship with St. Alphonsus de Liguori and his apostolate. Together they devoted themselves to teaching the catechism to laypeople by organizing the Evening Chapels.
Following his ordination he was assigned by Cardinal Pignatelli as Director of Religious Instruction in the parish of Sts. Francis and Matthew in the Spanish quarter. Having become aware of the rampant corruption of young girls he decided to direct all his energy against prostitution. In the same period (1733) he tenaciously defended St. Alphonsus against unjust criticism after he had founded the missionary Congregation of the Most Holy Redeemer in Scala (SA) on November 9 1732. In June of the same year having gone to Scala to help his friend during the mission at Ravello, he decided to become a Redemptorist while at the same time continuing to be a member of the Apostolic Missions. From his entrance into the Congregation in April 1736 he committed himself unsparingly to parish missions and to writing in defence of "young girls in danger". He also wrote on the spiritual life and worked so hard that he was almost at death's door. With the consent of St. Alphonsus he returned to Naples for treatment and there renewed his apostolate for the rescue of prostitutes.
As well as taking part in the Redemptorist apostolate and that of the Apostolic Missions he promoted meditation in common among the laity by publishing "Il mondo santificato". He also campaigned against blasphemy in another book. In 1741 he planned and took part with St. Alphonsus in the great missions preached in the hamlets outside Naples in preparation for the canonical visitation of Cardinal Spinelli. Despite the permanently insecure state of his health he continued to preach until the end of April 1744 when by now extremely ill he returned to Naples where he died on June 30 at the age of 42. His body lies at rest in Ciorani, the first Redemptorist Church.
Gennaro Maria Sarnelli has left us 30 works which treat of meditation, mystical theology, spiritual direction, law, pedagogy, moral and pastoral themes. By his social action in favour of women he is considered one of the authors who treated this subject most fully in the Europe of the first half of the eighteenth century.
On May 12 1996, Pope John Paul II beatified him in St. Peter's Square.