Beatrice Culleton Mosionier, formerly Beatrice Culleton, is a Canadian Métis author, born in 1949 in St. Boniface, Manitoba. She is the youngest of four children. Because of her parents' alcoholism, when she was three years old, she became a ward of the Children's Aid Society. She grew up living in several foster homes separated from her brother and two sisters. Both sisters committed suicide and for emotional release, Beatrice turned to writing. She was a student at St. Charles Catholic School, and Gordon Bell High School where she completing Grade 11. She attended George Brown College in 1970 and Banff School of Fine Arts in1983.

Mosionier's first novel, In Search of April Raintree, was published in 1983. The story included traumatic incidents from her own family life, including the suicide of two of her sisters and her own experience of being raped.

Mosionier's second novel was published in 2000 and is titled In a Shadow of Evil. It is set in the Canadian Rockies, and follows the life of a young girl going through family trauma and foster care.

Her first children's book Spirit of the White Bison is told from the perspective of a young white bison. It portrays the fall of bison herds and the invasion of European settlers which are part of Canadian history.