Clonsilla (Irish: Cluain Saileach, meaning "meadow of the willow or sally tree") is a suburb of Dublin in the district of Fingal, Ireland. It is also a civil parish in the barony of Castleknock. Clonsilla is also a parish in the Blanchardstown deanery of the Roman Catholic Archdiocese of Dublin.
Clonsilla used to be a small village, 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.
The townland of Clonsilla is in the civil parish of Clonsilla which is in turn in the barony of Castleknock. The barony (an old administrative division) is one of seven and a half comprising County Dublin and stretches from Cabra to Blanchardstown (from east to west) and from Finglas to Chapelizod (from north to south).