Saint Dymphna is well known as a patron of people living with mental illness. She was a 7th century Irish princess who fled from her father, who seems to have had a mental illness, and she settled in Geel, Belgium, where she cared for people with mental illnesses. Because she lived so long ago, much of her story is shrouded in the mist of legend, so it is difficult to know with certainty much about Dymphna herself.
However, what is known with certainly is that Saint Dymphna’s legacy inspired the people of Geel to show compassion for people who live with mental illness. Over the centuries the people of Geel invited people with a mental illness to live and work in their community without any stigma or discrimination. Throughout the Middle Ages and even today the town of Geel is known as a model for community acceptance of people who live with a mental illness.
Feast Day - May 30 Official/May 15 Traditional
Dymphna was beheaded on 30 May, although the year of her death is uncertain. A transfer of her relics occurred on 15 May of a subsequent year,[3] the anniversary of which became her primary feast day until the 21st century, when the post-conciliar Roman Martyrology (the authoritative compendium of feast days for the Roman Rite of the Catholic Church) assigned Dymphna's feast to the anniversary of her martyrdom, on 30 May, as listed in the 2004 edition.
From 'Some Saints lived with mental illness’ - Vatican News, November 3, 2021