Saint Margaret Mary Alacoque was born on July 22, 1647 at L'Hautecour, in the province of Burgundy, France. As a child, she studied under the auspices of the Poor Clares at Charolles. Her father died when she was just 8 years old. She was bed-ridden with rheumatic fever from the age of 11 to 15. At this time, she was known as an ardent devotee of the Blessed Sacrament.
She joined the Order of Our Lady of the Visitation at Paray-le-Monial in 1671 and just a few years later received the unique favor of being visited by Our Lord Himself, who asked her to spread devotion to His Most Sacred Heart. This she humbly did, once she had received the permission and approbation of her superiors, especially her spiritual director and confessor, St.. Claude La Colombière.
In 1688, a chapel dedicated to the Sacred Heart was constructed at Paray-le-Monial and soon the devotion began to spread, with the help of the Visitandine Nuns and the priests of the Society of Jesus.
St. Margaret died on October 17, 1690. The devotion that Our Lord gave to the world through her was officially approved by Pope Clement XIII in 1765.
St. Margaret Mary Alacoque was canonized by Pope Benedict XV in 1920.source: sacredheart.com