13 May - Marie-Dominique was born on 9 May 1837 in Mornese in Piedmont to a family of farmers. She could not receive much education because there was no school in her village. It was her father who taught her the rudiments of reading and arithmetic.

She teaches catechism, gives free health care to the needy in the village, and joins a group created by Angela Maccagno in Mornese, a group of young girls who wish to live consecrated lives in the world, in the service of others. Mary Dominica is one of the five Daughters of the Immaculate who consecrated themselves to God in the presence of Fr Pestarino in 1855.

The parish priest, who was part of the Salesian congregation, asked her to found a school for girls according to the ideals of John Bosco. The small group around Mary Dominica would become the Congregation of the Daughters of Mary Help of Christians. Thus, in 1870, after a meeting with Don Bosco whom she chose as her spiritual director, Mary Dominica took her vows in 1871. In 1872 Don Bosco founded the branch of the Salesian Sisters of which Mary Dominica was the first superior.

She died at the age of forty-four while accompanying a group of missionaries who were taking the boat to Marseilles. Nine years after its creation, the Institute had more than one hundred religious sisters and about fifty novices in twenty-six communities. At present, the Salesian Sisters of Mary Help of Christians meet in many countries of the world.

Mary Dominica Mazzarello was beatified in 1938 by Pope Pius XI. She was canonized on June 24, 1951 by Pope Pius XII.