Grangegorman is a suburb on the northside of Dublin city, Ireland. The area is administered by Dublin City Council. It was best known for decades as the location of St Brendan's Hospital, which was the main psychiatric hospital serving the greater Dublin region. The area is currently the subject of a major redevelopment plan under the aegis of the Grangegorman Development Agency, including the launch of the main unified Dublin Institute of Technology (DIT) campus.

Grangegorman has evolved over time to its current boundaries, which, like those of most Dublin suburbs, are imprecise, while for the purposes of redevelopment, an extended "neighbourhood" was defined. A major historic feature was the Bradogue River, now culverted but still cutting right through the area on its way to the River Liffey.

Grangegorman is located in the Dublin 7 postal district, north of the River Liffey and about 1 km from Dublin city centre, and its boundaries run, approximately, along Brunswick Street North, Prussia Street and Manor Street, the North Circular Road and Phibsborough Road and Constitution Hill. Grangegorman is surrounded to the south east by Smithfield to the west by Stoneybatter, north by Cabra, to the north and east by Phibsborough / Broadstone.

The geographical definition of the north Dublin electoral division known as Arran Quay B, encompasses Grangegorman. The 2006 Census gives the population of Arran Quay B as 3,692. This represents a 19.5 per cent increase from the population of the area in 2002.