Helena Kowalska was born on August 25, 1905, in the village of Głogowiec in central Poland, the third of ten children. She worked as a domestic servant before entering the Congregation of the Sisters of Our Lady of Mercy in Warsaw in 1925, taking the name Maria Faustina. She served as cook, gardener and doorkeeper in the congregation's houses in Poland and Vilnius.
From 1931 she recorded in her Diary the revelations she received: the image of the merciful Jesus with two rays from his heart, the chaplet, the Hour of Mercy at three o'clock, and the request for a feast of Mercy on the Sunday after Easter. She died of tuberculosis at Kraków-Łagiewniki on October 5, 1938.
St. John Paul II beatified her on April 18, 1993, and canonized her on April 30, 2000, when he also established Divine Mercy Sunday for the universal Church. Her remains rest beneath the miraculous image in the convent chapel at Łagiewniki; the basilica beside it was consecrated by John Paul II in 2002.