It was designed from 1789 and laid out in 1792, on land belonging to the Pembroke estate,[3] which encompassed much of the area to the south-east of the city.

It was completed by 1830,[4] with progress slowed by the Acts of Union,[5] which led to a downturn in Dublin's prosperity due to an exodus of many wealthier residents to London.

The square was a popular place for the Irish Social Season of aristocrats entertaining in Dublin between January and Saint Patrick's Day each year.

[7] Sir Thomas O'Shaughnessy (1850–1933), the last Recorder of Dublin, lived in Fitzwilliam Square and died there on 7 March 1933.

[10] In 1975, Bord na Móna were granted permission to demolish five early 19th-century houses on the edge of the square, with plans to construct a modern office block on the site.