Jean Gailhac was born in Béziers, France, on November 13, 1802. He was ordained a priest in the Diocese of Montpellier in 1826. Shortly after his ordination, he requested of his bishop placement as chaplain of the civil and military hospital in the city of Béziers. This work, which he continued until the foundation of the Religious of the Sacred Heart of Mary in 1849, put him in contact with the most needy and marginalized of his society.

One of the groups whose needs became obvious to him was women who had fallen into a life of prostitution. In working with these women, he realized that most of them had no social or family support to assist them. Gailhac made arrangements for many of these women to be received in a shelter in Montpellier, paying their room and board from his own small salary, assisted by funds from his parents. When he could no longer afford the fees, he founded in Béziers the work of the Good Shepherd, a shelter for women and very soon afterwards, an orphanage as well.

The death of his good friend, Eugene Cure, in 1848 brought an unexpected turn to Father Gailhac's life. Appollonie Cure, widow of Eugene, expressed to him her desire to give her life and her wealth to his works. For a number of years Gailhac had considered founding a religious congregation. He saw Madame Cure's desire as a providential opportunity to do so.

Under Father Gailhac's direction, the Institute of the Religious of the Sacred Heart of Mary was founded in 1849. He worked closely with the community, especially with Mother Saint Jean (Appollonie Cure). The solid formation of the sisters became his primary focus. With them, he continued the various works in Béziers. As the Institute expanded, he communicated with the sisters at a distance through his numerous letters and visits. Toward the end of his life, he wrote treatises on a number of spiritual topics.

The death of the sisters always caused him great sorrow. He outlived the first two general superiors, Mother St. Jean and Mother St. Croix. He died on January 25, 1890 at the age of 88. In the 1950's, Mother Gerard Phelan introduced his cause of beatification. In 1972 he was declared Venerable by the Church.