Fingal (Fine Gall in Irish, meaning "foreign tribe", i.e. Norsemen) is formed from part of the historic county of Dublin. The Vikings referred to the area as Dyflinarskiri, the hinterland of Dublin. The original name, however, derived from the old Gaelic Fionn Gall meaning fair strangers, denoting the Norse, whereas south county Dublin was called Dubh Gall, denoting the occupying Danes. Early Anglo-Norman versions of the name include the similar Fiehengall, Fynnegal, Fyngal, and Finegal, which led to the mis-identification with Fine Gall. Fingalian is an extinct language, a hybrid of Old English and Old Norse, with Gaelic influences, which was spoken by the people of Fingal until the mid-1800s.

The first administrative identity going by a variant of the original name was the grant of the Lordship of Fingal, a Prescriptive Barony, confirmed by letters patent from King John to Walter de Lacy and his heirs in perpetuity, in 1208, and based on the latter's father Hugh de Lacy's holding the same on a basis of grand serjeanty for his services as bailiff to the King. The lordship of Fingal was a paramount superiority over several sub-infeudated smaller baronies (such as Castleknock, Santry, Balrothery), and thus eventually accrued vicecomital attributes leading to the granting of the first viscountcy in Ireland in 1478 to a Preston, Lord Gormanston, the Premier Viscount of Ireland, who at the time was the main landowner in the area, and a direct descendant of Walter de Lacy. That viscountcy was called after Gormanston as the latter was the principle seat and Manor of the Prestons at the time, having been acquired upon their relinquishment of occupancy of the Manor of Fyngallestoun. The Viscounts Gormanston continued to retain the Lordship of the latter under reversion.

In 1210, Fingal was included in County Dublin, one of the first twelve counties created by King John during the shiring of Ireland. Over the centuries, Fingal included several other baronies, namely Finglas, Feltrim, Howth, Shankill, Swords. A peerage title as Earl of Fingall was created in 1628, by King Charles I of England, and granted to Lucas Plunkett. The title went extinct upon the death of the 12th and last Earl in 1984, along with a peerage barony of the same name, not to be confused with the titular prescriptive barony of Fingal, long retained by the Viscount Gormanston as an incorporeal hereditament in gross.

The area of Fingal, which had been recognised in various historical accounts throughout the middle ages (most notably the Annals of the Four Masters), was raised to county status on 1 January 1994, through the Local Government (Dublin) Act, 1993 and more formally in the Local Government Act, 2001, with the division of old County Dublin into three new counties. Due to the Government’s failure to deliver on a promised media campaign that was to coincide with the county’s establishment, few people are aware of the idea of "County Fingal" and so to date, it has generally been referred to as "North County Dublin." It covers the coastal area north of City of Dublin along the Irish Sea and south of the River Delvin to the River Liffey, and it is bordered by the counties of Meath, Kildare and South Dublin.

Fingal is Ireland’s primary horticultural region, producing 50% of the national vegetable output and 75% of all glasshouse crops grown in the country. However, the areas of production are coming under severe pressure from other development and the rural towns are increasingly becoming dormitories for the City. Howth harbour is the biggest fishing harbour on the east coast and the fifth largest in the country.

Fingal itself is the fifth largest local government area in Ireland by population. The main urban center in Fingal is Blanchardstown with other important centres at Balbriggan, Castleknock, Howth, Malahide, Mulhuddart, and Swords. The Institute of Technology, Blanchardstown and Dublin International Airport are located within the county.