Mountjoy Square 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. Construction began in the early 1790s and the work was completed in 1818.

Located in the centre of Mountjoy Square the park was originally created by the Developer of the Square, Luke Gardiner, Lord Mountjoy around 1800, as part of his grand concept which envisaged the great sweep of Gardiner Street down to the Custom House. Today the park is in two distinct halves separated by a tall hedge. The western half remains as an open grass area, with the buildings and sports facilities concentrated in the eastern half. It is interesting to note that is the only true Georgian garden square in Dublin as it is the only one of the five Georgian squares to have four equal sides.

While the Square was upgraded in the late 1980s, its full potential as a Georgian Park must await the relocation of the existing all-weather sports area currently under active consideration by the City Council.

The council proposes to relocate the non-original facilities to other sites away from the historic square, reinstate the formal gardens and introduce tearooms and a bandstand at an indicative cost of up to €8.1 million.