Farmleigh is the official Irish state guest house. It was formerly one of the Dublin residences of the Guinness family. It is situated on an elevated position above the River Liffey to the north-west of the Phoenix Park, in Castleknock. The estate of 78 acres (32 ha) consists of extensive private gardens with stands of mature cypress, pine and oak trees, a boating pond, walled garden, sunken garden, out offices and a herd of rare native Kerry cattle. It was purchased by the Government of Ireland from the 4th Earl of Iveagh in 1999 for €29.2 million. A state body—the Office of Public Works (OPW)—spent in the region of €23 million restoring the house, gardens and curvilinear glasshouses, bringing the total cost to the state to €52.2 million. Farmleigh was opened to the public in July 2001.

The River Liffey is a river in eastern Ireland that ultimately flows through the centre of Dublin to its mouth within Dublin Bay. Its major tributaries include the River Dodder, the River Poddle and the River Camac. The river supplies much of Dublin's water and supports a range of recreational activities.