Délia Tétreault, founder of the first canadian missionnary institute, was born in Marieville (Quebec) on February 4, 1865, together with a twin brother who dies seven months later. At her mother’s death, when she is two years old, Délia is adopted by her uncle and aunt. She enjoys reading through the stacks of copies of the periodicals published by the Propagation of the Faith and the Holy Childhood Association that she finds in the attic and she dreams of becoming a missionary. For her education, her aunt enrolls her in a school run by the Sisters of the Presentation of Mary. At the age of thirteen, she begins to feel a calling to the religious life and at the age of fifteen she makes a vow of perpetual chastity.
When she is eighteen Délia asks to enter the Carmelite monastery of Montreal but they refuse her. She then applies to the Sisters of Charity of Saint-Hyacinthe, who accept her as a postulant. However her poor health soon obliges her to return to her uncle’s home, where she takes care of her aunt for several years. During this time, she meets a French Jesuit, Father Pichon, who asks her to help him establish an Institute devoted to help immigrants. For ten years, Délia helps Father Pichon in a poor neighborhood of Montreal: visits to the sick, catechesis, volunteer work occupy her life, but Délia still dreams to become a missionary.
She therefore quits the Institute to devote herself to her missionary project: the opening of an apostolic school for women preparing them to become missionaries. In 1902, it becomes the Society of the Missionary Sisters of the Immaculate-Conception. From then on she opens many missions in Canada, Asia, Africa, Madagascar, South America, and Central America. She also founds a lay women association for the mission (1905). Then, in 1921, she inspires Father Lapierre with the idea of founding a new Foreign Mission Society for priests and encourages him to approach the Bishop of Montreal.
In 1933, Délia becomes seriously ill. She dies on October 1, 1941, after eight years of great suffering. She is declared Venerable by Pope John-Paul II, on December 18, 1997.