Blanchardstown (Irish: Baile Bhlainséir) is a large outer suburb of Dublin in the modern county of Fingal, Ireland. Located ten kilometres (6 mi) northwest of Dublin city centre, it has developed since the 1960s from a small village to a point where Greater Blanchardstown is the largest urban area in Fingal.^{[citation needed]}

It is within the historical barony of Castleknock in the traditional County Dublin, as well as the Dublin 15 postal area and the Dublin West electoral constituency.

One of Ireland's largest shopping and leisure complexes — the Blanchardstown Centre and adjacent facilities — is located in the area.

The name Blanchardstown comes from the Blanchard family, who were granted their estate sometime between 1250 and 1260. The name 'Blanchard' is thought to come from the old French word 'blanch' meaning white, in turn potentially referring to white or fair hair.

Blanchardstown is just outside Dublin's M50 motorway semi-ring road, slightly to the north of the tolled crossing of the River Liffey. The core of the suburb is the townland of the same name, containing the village and the Roselawn housing area. It is bordered to the east by the suburb of Castleknock, to the west by Coolmine, which includes some areas, including the Blanchardstown Centre and surrounding retail parks, central to the district, and Clonsilla/Ongar, to the north by Tyrellstown and Hollystown, and to the south and south-east by Porterstown and Diswellstown. The stretch of suburban housing from Castleknock Way north to the Old Navan Road and Talbot Court, including Laurel Lodge, has an ambiguous status - all of it is in the townland of Blanchardstown. The townland has an area of over 454 acres and is within the historical Barony of Castleknock.

The River Tolka, the second river of Fingal, and Dublin, runs through the centre of the area, meandering to run just north of the village core, and then further north to pass the Connolly Memorial Hospital and then Abbotstown.

The Royal Canal and the Dublin-Sligo railway line pass along the southern edge of Blanchardstown proper from east to west.

Blanchardstown was a predominantly rural area, with a small village, in western County Dublin, alongside the neighbouring district of Castleknock. Both areas shared a common history until well into the 19th century, when their development diverged. In A Topographical Dictionary of Ireland, published in 1837, Blanchardstown is described as "a village [..] on the road to Navan, containing 57 houses and 342 inhabitants".