Glencullen is a village and townland in the county of Dún Laoghaire in south County Dublin, Ireland. It is in the civil parish of Kilternan and the barony and Poor Law Union of Rathdown.

The village is on the R116 road on the slopes of Two Rock Mountain, above the valley of Glencullen (from which it takes its name). Its highest point is at a height of about 300 metres (980 ft), making Glencullen one of the highest villages in Ireland.

There is a Bronze Age wedge tomb at Ballyedmonduff on the south eastern slope of Two Rock Mountain. It is known locally as the giants grave. It is a rectangular chamber divided into three parts surrounded by a U shaped double walled kerb filled with stones. The tomb was excavated in the 1940s by Sean P. O'Riordain and Ruaidhri De Valera when cremated bone, a polished stone hammer, flints and pottery were found.

Below Two Rock Mountain is the prominent South Dublin landmark of Three Rock Mountain, complete with its Communications Masts, some of which are visible from Glencullen.

Glencullen also has an important standing stone at Newtown Hill and also has an earthern burial mound dating from the same period as the wedge tomb at Ballyedmonduff.

At the centre of the village is Johnnie Fox's Pub, which was established in 1798, the year of the Irish Rebellion led by Theobald Wolfe Tone. It is claimed to be the highest pub in Ireland – a claim disputed by other pubs in Ireland. It was used by the 1916 Rebellion leaders as a meeting place.

The number 44B Dublin Bus service runs from the Dundrum Luas station to Glencullen.