Gagnard was born in Poncins, Loire, Auvergne-Rhône-Alpes, France, on 29 October 1899, as the eldest daughter a family of eight children. Her mother died at the age of 98.
On 24 April 1928, at the age of 28, she married Étienne Gagnard, a sawyer. The couple moved to Feurs, where they operated a café. They had four children, two daughters (one of whom, Lucette, died as a child on Christmas Day 1931) and two sons. At the age of 100, she moved into a nursing home.
Gagnard passed away in Feurs, Loire, Auvergne-Rhône-Alpes, France, on 14 August 2010, at the age of 110 years, 289 days.
Her age was validated by the Gerontology Research Group on 2 February 2010, and later by the ESO on 24 October 2022.
* “Jeanne Gagnard, 110 ans aujourd’hui : La doyenne de la Loire est forézienne” – Le Progrès, 29 October 2009
* “La doyenne des Foréziens, Jeanne Gagnard fête ses 110 ans” – Le Petit Forézien, December 2009
* “Madame Jeanne Gagnard (110 ans)” – Commune de Poncins, 4 January 2010