Clonsilla is an outer suburb of Dublin in Fingal, Ireland. Clonsilla is also a civil parish in the barony of Castleknock in the traditional County Dublin. Clonsilla used to be a small village in the inner western part of County Dublin, but it is now a large residential suburban area, with Ongar and other localities developing their own subsidiary identities. It falls into t…Clonsilla is an outer suburb of Dublin in Fingal, Ireland. Clonsilla is also a civil parish in the barony of Castleknock in the traditional County Dublin. Clonsilla used to be a small village in the inner western part of County Dublin, but it is now a large residential suburban area, with Ongar and other localities developing their own subsidiary identities. It falls into the Dublin 15 postal district, the Dublin West Dáil constituency and is locally administered by Fingal County Council.