Stenbäck was born in Lumparland, Åland Islands, Finland (then Russian Empire), on 21 September 1914, to parents Paul Sivard Stenbäck (1880–1965) and Hulda Cecilia Sofia Isaksson (1888–1953). She had three sisters: Lempi Cecilia (1908–1970), Maj-Lis Sofia (born 1918), and Lea Charlotta. She also had three brothers: David Natanael (1909–1983), Gustav Bernhard Samuel (1911–1994), and Asser Immanuel (1913–2006).
In 1933, she graduated from Kotka Lyceum High School. That same summer, during a Christian summer gathering in Kokkola, she discovered her life mission and calling. She received an invitation to apply to the Deaconess Institute, and the following year, she began her studies at the Helsinki Deaconess Institute’s Nursing School. In 1943, she was ordained as a deaconess and served in that role for about ten years with the Swedish-speaking congregation of Sörnäinen. Her interest in the care of individuals with mental disabilities led her to study trips in Europe and America in the 1950s, initially as a scholarship recipient. Later, her travels took her to nearly 50 countries around the world.
In 1956, Sister Gunnel was appointed head nurse at Rinnekoti, an institution for individuals with intellectual disabilities run by the Deaconess Institute. During the following decade, she pursued social policy studies at the University of Helsinki, earning her licentiate degree in political science in 1969. That same year, she was named Principal of Helsinki Diakonia College, the very school where she had begun her studies in 1934, though the school had undergone several name changes. A few years later, she was appointed director of the Deaconess Institute, a position she held until her retirement at the end of 1977.
At the end of August 2024, Bishop Teemu Laajasalo of the Diocese of Helsinki visited her at the nursing home, where an early celebration was held for her upcoming 110th birthday. The event was also attended by Olli Holmström, CEO of the Deaconess Institute, along with the nursing home staff.
Gunnel Stenbäck passed away in Helsinki, on 30 November 2024, at the age of 110 years, 70 days.
On 12 June 2024, following the passing of 110-year-old Helvi Kissala, she became the oldest living person in Finland, at the age of 109 years, 265 days. However, she was not the oldest living person born in Finland, as that title belonged to Gunborg Hancock, who resided in Sweden.
By celebrating her 110th birthday, she became only the second supercentenarian born in the Åland Islands, alongside Anna Hagman (1895–2006).
Her age was verified by Jimmy Lindberg, and validated by the European Supercentenarian Organisation (ESO) on 22 September 2024, and by LongeviQuest on 28 September.
On 16 October 2024, following the passing of 112-year-old Gunborg Hancock, she became the oldest living Finnish-born person, at the age of 110 years, 110 years, 25 days.
* Gunnel Margareta Stenbäck – Geneanet
* “Suomen todennäköisesti vanhin ihminen täyttää 110 vuotta – syntymäpäiville ilmestyi yllättävä vieras” – Ilta-Sanomat, 20 September 2024
* “Sisar Gunnelin elämänkaari on ollut pitkä ja monipuolinen” – Diakonissalaitos, 21 September 2024
* “Suomen vanhin henkilö sisar Gunnel täyttää 110 vuotta – teki elämänsä suuren valinnan vuonna 1959” – MTV Uutiset, 21 September 2024
* “Suomen tiettävästi vanhin ihminen on kuollut 110-vuotiaana” – Helsingin Sanomat, 1 December 2024