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Formerly named Rutland Square, it was renamed after Charles Stewart Parnell (1846–1891), as was Parnell Street, which forms the southern side of the square. Surrounded on three sides by terraces of original intact Georgian houses, much of the southern part of the square and its centre is taken up by extensions of the Rotunda Hospital. The Garden of Remembrance is located along the northern side of this area. Its main entrance is on the eastern side of the square, with a smaller entrance on the northern side of the square.
In the south easterly corner of the square, where it meets with O'Connell Street, is sited the Gate Theatre, and the Ambassador and Pillar Room venues. Entertainments were originally developed here as part of the Rotunda Hospital scheme by Bartholomew Mosse as a revenue engine to pay for the running of what was Europe's first lying-in maternity hospital. Extensive pleasure gardens, subsequently forming the body of the square, were located to the rear of the hospital in the original development.
The Hugh Lane Gallery is on the north side of the square. It was erected in cut stone by Lord Charlemont to a design by William Chambers during the Georgian period. On this side also is the Dublin Writers Museum and the Irish Writers' Centre. The striking Gothic Revival Findlater's Church (Abbey Presbyterian Church) just up from the gallery on the same side was erected in the 1860s by Alexander Findlater, at his own expense, and which he presented to the Presbyterian congregation. The James Joyce Centre is located nearby on North Great Georges Street, a street notably rich for its Georgian houses as is the nearby and historic Mountjoy Square. One of Dublin's most acclaimed restaurants, Chapter One, is located on the northern side of Parnell Square between the Hugh Lane Gallery and the Writers Museum. On the south side of the square is Conway's bar, outside of which Pearse surrendered to the British army after the 1916 Easter Rising. The political party Sinn Féin has its Dublin head office and shop on the western side of the square. The western side also is known for offices of a number of trade unions and other organisations. Also on the western side is the St. Martin's Apostolate office, which includes a small basement chapel. The St. Martin's Apostolate office is well known in Dublin for its moving crib that is open to the public each Christmas.
Famous historic residents and events 
No 5 – Birthplace of Oliver St John Gogarty (1878–1957); writer, surgeon, and senator. A friend of Michael Collins and the writers WB Yeats and James Joyce, Gogarty was unwillingly immortalized as Buck Mulligan in the Ulysses.
No 9 Cavendish Row – Dr Bartholomew Mosse (1713–1759); Philanthropist and surgeon. Mosse lived here, having originally hailed from Portlaoise. He founded the Rotunda Hospital, located in the square and which was built to designs of Richard Cassels between 1751 and 1757. The emergence of Parnell Square as a square is largely attributable to the pleasure gardens him as he laid out pleasure gardens in order to pay for the hospital. No. 14 Parnell Square was the headquarters of Conradh na Gaeilge in the 1940s and 1950s and perhaps into the 1960s. The Ard Chraobh of the Gaelic league was in this building. No 25 Parnell Square, Gaelic League Building. This building is of great significance during the period surrounding the War of Independence as it was here on September 9, 1914 that a meeting held by Supreme Council of the Irish Republican Brotherhood (IRB) with selected others agreed to rise up against the British before the Great War, subsequently known as the First World War, would be finished: In attendance were Eamonn Ceannt, Thomas Clarke, James Connolly, Arthur Griffith, John McBride, Sean MacDermott, Sean McGarry, William “Bill” O'Brien, Seán T. O'Kelly, Padraig Pearse, Joseph Plunkett.
No 29 – 30 Parnell Square – Formerly Vaughan’s Hotel; a favourite hiding and meeting place for freedom fighter Michael Collins.
No 41 Parnell Square – this building was formerly the Irish National Forester’s Hall. Prior to 1916 it was used for drilling both by the Irish Republican Brotherhood (IRB) and the Volunteers; on the eve of the outbreak of the Easter Rising Éamon de Valera assembled the 3rd Battalion here. In 1922, subsequent to the Treaty and prior to the Civil War, the IRB again met here in a failed attempt at achieving consensus on the Treaty; among the attendees were Michael Collins, Harry Boland, Liam Lynch and Eoin O'Duffy – all of whom, with the exception of O’Duffy, were dead by the end of the Irish Civil War.
No 46 Parnell Square – Formerly the Headquarters of Conradh na Gaeilge, the Irish language league, this was the venue where Thomas MacDonagh assembled the 2nd Battalion the Sunday night on the eve of the 1916 Easter Rising. In August 1917, the meetings that led to the National Executive of the Irish Republican Army being established were also here, with persons present including Éamon de Valera, Thomas Ashe, Cathal Brugha, and Michael Collins. Subsequently on September 19, 1919, in the company of Richard Mulcahy, Michael Collins set up his famous “Squad”, composed of top-level operatives – men who would ultimately be involved with highest priority missions, such as the elimination of the British “G Men” agents in 1920.
No 58 Parnell Square - The Sinn Féin Bookshop and the offices of the An Phoblacht newspaper.