Merrion Square, also known as Cearnóg Mhuirfean in Irish, is a Georgian-style garden square located in the southern area of the city center.

This square was designed in 1762 by John Smyth and Jonathan Barker as part of Viscount FitzWilliam's estate. Subsequently, Samuel Sproule added the east side around 1780, and the gardens were created through a competition won by Benjamin Simpson in 1792 based on the designs of John James Barralet. Most of the houses around the square were completed in the 19th century, after a lawsuit prompted by the construction of Leinster House, the largest aristocratic residence in the city, by the then Earl of Kildare and later Duke of Leinster.

In terms of heritage, most of the original 18th century properties in Merrion Square have survived, with the exception of Antrim House, which was demolished in the 1930s to make way for the National Maternity Hospital. The square is surrounded by red-brick Georgian townhouses on three sides, while the west side abuts Leinster House, government buildings and several important museums. The central garden is enclosed and currently functions as a public park.

Initially, it was planned to erect the Wellington Monument in Merrion Square to commemorate the victories of Arthur Wellesley, but due to opposition from residents, it was eventually placed in Phoenix Park.

As for the current use, although in the past the houses in the square were mainly residential, today most are used as offices. Several important organizations are based in the square, and figures such as Oscar Wilde, William Butler Yeats and Daniel O'Connell have lived at different addresses in the square.

Merrion Square Park, formerly accessible only to residents with a key, is now managed by Dublin City Council and houses a statue of Oscar Wilde, additional sculptures, and a collection of historic lampposts. Although initially named Archbishop Ryan Park, it was renamed Merrion Square Park in 2010 after a public consultation due to controversies related to Dermot Ryan, who gave the land to the city council.