Saint Nissen was an early Christian convert who was abbot of a monastery in County Wexford, Ireland.
Saint Nissen was converted to Christianity by Saint Patrick. He became abbot of Montgarth (Mountgarret) Abbey in Wexford, Ireland. His feast day is 25 July.He is additionally celebrated on 24 July in the Orthodox Church
The monks of St Augustine's Abbey, Ramsgate, wrote in their Book of Saints (1921),
The hagiographer Alban Butler ( 1710âÂÂ1773) wrote in his Lives of the Primitive Fathers, Martyrs, and Other Principal Saints, under April 9,