Ballymun is an outer suburb of Dublin, Ireland, at the northern edge of the Northside, the green-field development of which began in the 1960s to accommodate a housing crisis in inner city areas of Dublin. While the newly built housing was state-of-the-art at the time, comprising high-rise tower blocks and flat complexes, residents were moved in years before shops, schools and other infrastructure were fully ready, and the area became well known for both a strong community spirit and considerable social challenges. Ballymun has several sub-districts such as Sillogue, Coultry, Shangan and Poppintree, and is close to both the Republic of Ireland's only IKEA store and to Dublin Airport. The area is the source of one Dublin river, and parts lie in the floodplain of another, and there are a number of parks.

The Northside in an informal but commonly used term to describe the part of the city of Dublin that lies to the north of the River Liffey, and extending into part of North County Dublin. The part outside the city is within the county of Fingal, a local government area established in 1994. While it is sometimes regarded as less wealthy than the city's Southside, the Northside was originally the home of the city's upper classes and the more privileged of the two. Today, some of the wealthiest areas in Ireland, such as Malahide, Howth, Clontarf, and Castleknock, lie north of the river.