Mountjoy Square (Irish: Cearnóg Mhuinseo) is a Georgian garden square in Dublin, Ireland, on the north side of the city just under a kilometre from the River Liffey. One of five Georgian squares in Dublin, it was planned and developed in the late 18th century by the Luke Gardiner, 1st Viscount Mountjoy. It was surrounded on all sides by terraced, red-brick Georgian houses.