Stephanie Jean Castle (born December 28, 1925 – May 8, 2017) was a Canadian transgender activist, author, and publisher. She was a prominent figure in the early Canadian transgender rights movement and is best known as the co-founder of the Zenith Foundation, one of Canada's first advocacy and support organizations for transgender people.

Castle was born in Hoylake, Cheshire, England. In 1943, during World War II, she enlisted in the Royal Navy, serving as a midshipman and later as a sub-lieutenant in the Royal Naval Volunteer Reserve. She served in the Pacific Theatre and stayed in the South China Sea for 18 months following the surrender of Japan.

In 1947, she left the Navy and began working in marine insurance. In 1952, she immigrated to Canada, settling in Vancouver, British Columbia. Over the next several decades, she built a successful career as a marine insurance underwriter, shipowner, and real estate developer specializing in waterfront properties. She retired from her business career in 1990.

Castle began her gender transition when she was 62 years old. Following her transition, she decided to dedicate her life to transgender advocacy and education.

In 1992, Castle co-founded the Zenith Foundation with Christine Burnham and Dr. Patricia Diewold (a clinical psychologist at the Vancouver General Hospital Gender Clinic). The foundation was created to provide support and political advocacy for "transsexuals" (the terminology most common at that time).

Castle served as the editor of the foundation’s publications, including the Zenith Bulletin and the Zenith Digest. These publications were lifelines for the community. Circulating throughout Canada and beyond, these publications reached countries such as the United States, the UK, and Australia.

Castle was a key figure in pushing for legislative changes in British Columbia. Through the Zenith Foundation, she acted as an intervener in the landmark Canadian Human Rights Tribunal case involving Synthia Kavanagh and the Correctional Service of Canada, which fought for the rights of incarcerated trans women to access medical care and be housed in appropriate facilities.

Castle was a prolific writer, publishing over 30 books through her own Perceptions Press (later known as Stephanie Castle Publications). Her work encompassed both non-fiction educational guides and fiction that centered on transgender experiences.

• Feelings: A Transsexual's Explanation of a Baffling Condition (1992) – A seminal memoir and educational text.
• The Zenith Experience (2005) – A history of the Zenith Foundation and the early trans movement in B.C.
• Prisoner of Gender (1997) – Co-authored with Katherine Johnson.
• The Cascade Series – A series of fiction novels exploring the lives of transgender characters in the Pacific Northwest.

Castle died in Vancouver on May 8, 2017, at the age of 91. Her personal correspondence and the archives of the Zenith Foundation were donated to the Transgender Archives at the University of Victoria (UVIC), where they form the Stephanie Castle fonds. Her records are considered an important resource for the study of transgender history in Canada.

• Zenith Foundation
• University of Victoria Archives

1. "Stephanie Castle (1925-2017)". University of Victoria Transgender Archives.
2. Wilson, Margot. Girl in the Dream: Stephanie (Sydney) Castle Heal, A Transgender Life. TransGender Publishing, 2018.
3. "Transsexuals seek more respect, with help of rights commission". The Vancouver Sun, November 18, 1997.
4. "Stephanie Castle fonds". University of Victoria Archives, Reference code: CA UVICARCH AR422.