Mary Helen MacKillop, known in religion as Mother Mary of the Cross, was born on January 15, 1842, in Fitzroy, Melbourne, Australia, to Scottish immigrants Alexander MacKillop and Flora MacDonald. As the eldest of eight children, she assumed significant family responsibilities early on, especially due to the family's financial struggles. At 16, Mary began working as a clerk in Melbourne and later as a governess for her relatives in Penola, South Australia, where she educated both her cousins and the children of the local area. It was in Penola that she met Father Julian Tenison-Woods, a pivotal figure in her life's mission.

In 1866, responding to the educational needs of rural children, Mary and Father Tenison-Woods founded the Sisters of St Joseph of the Sacred Heart, Australia's first Catholic religious order established by an Australian. The order was dedicated to the education of the poor, particularly in remote areas, and emphasized a life of poverty and service. The sisters opened numerous schools across Australia and New Zealand, providing free education to those who had little access to learning. Despite facing challenges, including her brief excommunication in 1871 due to misunderstandings with church authorities—a decision later reversed—Mary remained steadfast in her commitment to her faith and mission.

Mary MacKillop passed away on August 8, 1909, in North Sydney, leaving behind a legacy of compassion, resilience, and dedication to social justice. Her life's work led to her beatification by Pope John Paul II in 1995 and her canonization as Australia's first saint by Pope Benedict XVI on October 17, 2010. Today, her feast day is celebrated on August 8, and she is revered as a patron of Australia, the Archdiocese of Brisbane, and the Knights of the Southern Cross.