Mary Domenica Mazzarello was born at Mornese, Alessandria (Italy) on 9 May 1837, the eldest of seven children of a hard-working peasant family of sincere Christian life. At the age of 15 years she offered herself to God with a vow of virginity. Soon afterwards she joined the association of the Daughters of Mary Immaculate, committing herself more deeply in apostolic services and works of charity.
A meeting with Don Bosco in 1864 marked a decisive point in her life. The Saint was already working on an apostolic project for girls, and with the collaboration of Mary Domenica gave rise to the community of the Daughters of Mary Help of Christians. In 1872 Mary Domenica made her religious vows and was elected superior, a role in which she displayed unexpected talents as a mother and animator.
On 14 May 1881, when only 44 years of age, she died at the new Mother House of Nizza Monferrato, Asti. She was canonized by Pius XII on 24 June 1951, and was rightly recognized as Co-foundress of the Institute of the Daughters of Mary Help of Christians.