Margaret Alacoque was born to a notary of the small Burgundian village of Lhautecour in 1647. Her father died when she was eight; she was sent to be educated by the Poor Clares at Charolles, where at eleven she fell ill with what was probably rheumatic fever or polio and was bedridden for four years. She vowed her virginity to the Blessed Virgin Mary and was cured.
She felt called from her earliest youth to religious life, but the family — under the iron rule of relatives who controlled the small estate — forbade it. For ten years she suffered relentless pressure to marry. In 1671, at twenty-four, she at last entered the Visitation convent of Paray-le-Monial in Burgundy and took the religious name Margaret Mary.
Between December 1673 and June 1675, she received four great apparitions of the Sacred Heart of Jesus while praying before the Blessed Sacrament. Christ showed her His Heart, surrounded by a crown of thorns, encircled with flames, and surmounted by a cross — and entrusted her with the mission of spreading the devotion to the Sacred Heart throughout the Church. He revealed twelve specific promises to those who would honor His Heart, and asked specifically for the institution of a Feast of the Sacred Heart on the Friday after the Octave of Corpus Christi, and for the practice of Holy Communion on the First Friday of each month for nine consecutive months.
At first she met disbelief and ridicule, even from her own community. Her director, the Jesuit St. Claude de la Colombière (1641–1682), recognized the authenticity of the revelations and became her chief defender. After her death the devotion spread quickly; Pope Pius IX extended the Feast of the Sacred Heart to the universal Church in 1856; Leo XIII consecrated the entire human race to the Sacred Heart in 1899. Margaret Mary was canonized in 1920. Her body, found incorrupt at her exhumation in 1830, rests in a gold and crystal reliquary in the chapel of the apparitions at Paray-le-Monial.