St John's parish, Clontarf was formed in 1966 when it separated from the historic Parish of Clontarf. The parish is in the Fingal South East deanery of the Roman Catholic Archdiocese of Dublin. It is served by a Church of St John the Baptist on Clontarf Road. This building is the modern site of a building that had existed in Clontarf, Dublin for centuries. It was funded by a legacy and opened in 1825 on the site of the locality formerly known as "the Sheds", an area of fish curing facilities and mud cabins.
The parish takes in the main centre of modern Clontarf, where Vernon Avenue meets the coast road, and from Castle Avenue near Killester to Dollymount, and then around Dollymount to Saint Anne's Park. It has a population of over 7,000. Near to the parish church is a convent and school of the Sisters of the Holy Faith.