Saint Margaret Mary Alacoque was born on 22 July 1647 at L' Hautecour, France. While she was a cheerful, intelligent little girl, she liked to hide herself in her private chapel and pray innocently. Since her childhood, she had dedicated herself to Jesus.
On 20 June 1671, she entered the Visitation Convent at Paray-le-Monial at the age of 23, and was professed the next year. On 6 November 1672 she pledged to devote herself to Our Lord. On that day she laid down a series of commitments in pursuit of a holy life, one of which was: "I will do everything for God, not for myself; I will always act according to God's will, not mine."
In the first half of the year following December, 1673, she experienced visions of Christ who informed her that she was His chosen instrument to spread the love of Christ to every corner of the world. One late night while she was praying, God revealed Himself to her with His Sacred Heart. "Here is my big, loving Heart, yearning for the repentance of mankind," He said to her. Since that revelation, she had taken great pains to establish the feast of the Sacred Heart despite opposition from a group of theologians under the influence of the negativity of Jansenism. She opened the hearts of many to the boundless compassion of our Lord.
She died on 17 October 1690. She left her last word during her final moment, "I am willing to immerse myself totally in the Sacred Heart of Jesus Christ." Observation of the feast of the Sacred Heart was officially recognized by Pope Clement XIII in 1856. She was canonized as a saint in 1920.