Sister Sue Mosteller, CSJ, OC (1933-) was born in Ohio to Canadian parents. In eighth grade, Sue Mosteller was sent to boarding school with the Sisters of St. Joseph in Toronto. Her experience boarding with the Sisters of St. Joseph led her to join the order upon graduating high school. After joining, Mosteller was encouraged to teach by the sisters and spent 15 years teaching in Barrie, Kitimat, and Toronto.
In 1967, when Sue Mosteller was finishing her BA in English Literature, her friend took her to a lecture by Jean Vanier at the University of St. Michael’s College where he talked about L’Arche and life living with the disabled. Vanier’s talk moved Mosteller and she assisted with organizing a pilgrimage to Lourdes for people with disabilities, their families, and young people. These experiences were a turning point for Mosteller and in 1972 she requested and received permission to live and work at L’Arche Daybreak, the first L’Arche community in Canada. Mosteller quickly became an integral part of the L’Arche community and oversaw many large initiatives. In 1976, Mosteller became L'Arche Daybreak’s second community leader. In the mid-1980s, Mosteller was instrumental in inviting Henri Nouwen to join the Daybreak community as their pastor. In 1985, Mosteller established Dayspring Chapel, a centre for spiritual growth, with Henri Nouwen. Beyond the Daybreak community, Mosteller served as the first international coordinator of L'Arche after Jean Vanier for nine years. During that time, Mosteller expanded the L'Arche network from 30 to 65 countries.
Over the ten years Henri Nouwen was at Daybreak, Mosteller and him became close friends. In 1996, Mosteller was asked by Nouwen to be his literary executrix of his estate shortly before his death. As executrix, Mosteller oversaw the founding of the Henri J.M. Archives and Research Collection at the John M. Kelly Library at the University of St. Michael’s College in Toronto. Mosteller would continue to live within the Daybreak community for 40 years until 2011 when she left to live with a small group of sisters in a Toronto Convent.
On November 5, 2011, Mosteller received an Honorary Doctorate from Tyndale University College and Seminary in Toronto for her “lifelong commitment to sharing the love of God with many of society’s marginalized people and her significant contributions to Christian life and learning over several decades.”
On December 27, 2019, Mosteller was named to the Order of Canada for her dedication to improving the lives of people with intellectual disabilities, and for her decades of work as a leader of L’Arche.
Today she continues to be a member of L’Arche Daybreak, works as a Trustee for the Henri Nouwen Legacy, and gives retreats and lectures all over the world.