Creideamh Sí thumb|right|Hawthorn tree, considered in local Irish lore (and Celtic folklore in general) to be sacred to the aos sí Creideamh Sí is Irish for the "Fairy Faith", a term for the collection of beliefs and practices observed by those who wish to keep good relationships with the aos sí and avoid angering them. General belief in the Celtic otherworld, the existence of aos sí and the ability of the aos sí to influence the local area and its people are all beliefs characteristic of the Creideamh Sí. It is characterised as an aspect of Irish popular religion and exists syncretically with folk Christianity.
Creideamh Sí thumb|right|Hawthorn tree, considered in local Irish lore (and Celtic folklore in general) to be sacred to the aos sí Creideamh Sí is Irish for the "Fairy Faith", a term for the collection of beliefs and practices observed by those who wish to keep good relationships with the aos sí and avoid angering them. General belief in the Celtic otherworld, the existence of aos sí and the ability of the aos sí to influence the local area and its people are all beliefs characteristic of the Creideamh Sí. It is characterised as an aspect of Irish popular religion and exists syncretically with folk Christianity.